One of the most stressful episodes of my career so far was when I had to collaborate on a project with a passive-aggressive colleague. We didn’t argue or fight or shout; the animosity was played out by my emails going unanswered, my direct questions being ignored, and my calls being directed to voicemail.

Passive aggression is so subtle, so under the radar, so impossible to put your finger on, that it’s no wonder that business leaders have called it ‘the perfect crime’.

[The secret to beating stress, whatever your age]

It’s not the sole preserve of working environments either; it can take the shape of the sullen shop assistant, the stomping, door-slamming teenager or the surly spouse giving you the silent treatment after a row. It can be particularly bad during festive occasions, when time with extended family and in-laws can cause resentment to fester under a facade of enforced bonhomie.

While it comes in many forms, the secret to its success is that it’s impossible to nail down. So it continues to lurk uncomfortably under the surface in our daily lives, like scattered landmines that we tiptoe around because we worry about the anger underneath them exploding in our face.

Getting to grips

Finally, though, it seems something is about to change. US-based therapist and social worker Signe Whitson is one of the world’s leading experts on interpersonal relationships. She is also co-author of the book The Angry Smile: The Psychology of Passive-Aggressive Behavior in Families, Schools, and Workplaces. While she admits getting to grips with passive-aggressive behaviour is as difficult as ‘nailing jelly to a wall’, Whitson has now designed an online course to tackle it head-on.

To be honest, I am so sick of dealing with it day in, day out, whether it’s ‘feigned misunderstandings’ (the other day a PR flatly claimed not to understand what I was asking for FOUR times, even though we were both speaking English) or convenient ‘temporary deafness’ from my husband and teenage children at home, that I can’t sign up quickly enough.

Who wouldn’t fork out around Dh800 for the promise of being able to end ‘endless conflict cycles, frustrating arguments and relationship-damaging wars of words’? The course is a three-hour, nine-module programme, which you can take at your own speed.

Each module contains a video – cheerfully led by Whitson, half amused/half exasperated on our behalf – explaining the different levels of passive aggression and how to deal with it.

After each, there’s a summary and a quick online test to check you’ve digested all the devious ways it works.

However it bubbles up, Whitson explains that what all passive- aggressive behaviour has in common is that the person concerned doesn’t like the power or influence you have over them – whether it’s a boss, parent, client, customer, colleague or partner. Or they simply resent what you are asking them to do.

In these relationships, they know they are not supposed to express anger openly, so it gets buried. It then surfaces in more subtle ways, which are difficult for you to confront. If you do ask them if there’s a problem, they can deny it.

The first step, says Whitson, is to identify what you are dealing with. Otherwise, you can get dragged into the ‘passive-aggressive conflict cycle’.

This is when you get so wound up by the drip-drip-drip of passive-aggressive behaviour that you start responding in kind. In the workplace, for example, this is when you start masking your own irritation with a colleague who won’t respond to an email with remarks such as ‘Please advise’ or ‘As per my last email’.

If you get sucked into this, Whitson warns that it will only escalate your frustration until you explode – and conveniently you will be the one who ends up looking like you have the anger problem.

‘If you are the target,’ Whitson explains, ‘you often don’t realise the amount of anger you are absorbing. You eventually spill over, the dam breaks. Then you get branded the crazy one. ‘The cycle continues because the passive-aggressive colleague then feels justified in keeping all their anger under wraps the next time, too.’

How to call it out

The killer question, of course, is how to call it out for what it is – without starting a row. The key lies in a process called ‘benign confrontation’. Whitson says: ‘Anticipate what’s going to happen and tell yourself, “This will be challenging, but I can handle it because I’m aware of this other person’s underlying anger”.’

Now to defuse it. The trick, she explains, is not to raise the hostility level but to quietly ‘affirm the anger’.

Don’t be confrontational or meet the passive aggression with outright aggression. Instead, quietly and firmly let the angry person know that you recognise their annoyance, starting with the phrase: ‘It seems to me you are angry that...’ Then leave it there. You don’t even have to know why they are angry, says Whitson. Shining a light on that feeling – like opening the vampire’s coffin – is enough to defuse its power.

As she says: ‘The idea is for the person to understand that their anger is not a secret any more.’ Here, the element of surprise will be on your side. As Whitson points out: ‘It’s likely that the passive-aggressive person has spent their time guarding and disguising this emotion, and has never had anyone name it directly.’ Expect immediate denials, she warns. When your nemesis says they have no idea what you are talking about, tell them blithely that it was just a thought you wanted to share with them – and you are relieved that’s not the case. Then leave it there. Remind them of the conversation if it happens again, so they know that you’re keeping an eye out.

‘They will have to relate to you on a different level from now on. Finally, say something conciliatory to confirm that you are ready to continue the relationship on a different footing – along with some clear expectations.’

At the end of the course, I score a satisfying pass on a 20-question exam and get a certificate adorned with lots of swirly writing to download.

I consider framing it and hanging it on my bathroom wall for any visiting family and friends over the festive period.

But that, of course, might just be seen as passive-aggressive behaviour in itself.

Deal with passive-aggressives without losing your mind

Acknowledge strengths: Pas-aggs tend to feel unappreciated. Defuse their anger by complimenting them on what they do well.

Apply the rule of three: Email is a godsend for passive aggressive people because it allows them to ignore you and pretend that they "didn’t see" your messages or to claim that they didn’t "have time" to respond. One unanswered email could be a mistake. Two is annoying. Three, and it’s time to inquire politely if there’s a reason for the underlying anger or resistance.

Face up to it: Each time you respond to passive aggressive behaviour, you reinforce it. Of course, often it’s wise to walk away. But if you have no choice, tackle it directly and assertively.

To sign up to the Angry Smile Course developed by Dr Nicholas Long and Signe Whitson, go to lsci.org/courses/the-angry-smile.