Private Investigator says you should 'never ignore' one thing if you think your partner is cheating on you

When you have a suspicion your partner has been unfaithful, it can sometimes be difficult to find proof of their infidelity, especially if they've covered their tracks.

However, there are a number of clues to keep an eye out for - with one particular sign being an immediate red flag.

The most common signs include spending more time at work, defensiveness and less affection or sex, as well as sudden changes in habits or interests.

Obviously, social media provides an easy method of finding out about unfaithfulness a lot of the time, with people turning detective to uncover their spouse's actions.

Some even turn to the professionals for help and hire private investigators to get to the bottom of any suspicions.

Tom Martin, a top private investigator, has revealed the biggest red flags to watch out for - and there's one that should never ignore.

There are certain signs to watch out for if you think your partner is cheating. (Getty Images)

Tom told The Independent that one of the most important signs is intuition, as people can generally tell when their partner is cheating on them and not being truthful.

Alongside relying on your intuition, there are a number of other clues to be aware of, including leaving the house earlier than usual, buying mystery gifts, secretive text messages, short temper and more.

In his book, Seeing Life through Private Eyes, Tom - also a former federal agent - lists the 20 most telling clues that may point to infidelity and advises readers that if they spot four or more, their partner is likely to be guilty of playing away.

However, noticing only one or two clues is generally not a cause for concern.

Tom explained that the majority of cheaters tend to follow a similar pattern, therefore it can be beneficial to be aware of the signs and noticeable changes to behaviour.

Among the 20 clues is missed phone calls from an unknown number, joining a gym, scent of somebody else, extra grooming and secret social media accounts.

Being absent from family events or holidays can also indicate unfaithfulness, as can obvious lies, hating surprise visits and signing up for excessive overtime at work.

There are a number of subtle clues that give away if your partner is being unfaithful. (Getty Images)

Tom also noted that social media has made catching cheaters much easier, and people are less likely to turn to private investigators for assistance now.

Being able to check somebody's phone for messages and calls, or noticing new faces on their social media accounts can allow people to uncover what their partner is up to with ease.

Tom said: “The game has changed drastically. And technology is 100 per cent the reason why.”