British adults are hiding their outgoings on things like beauty products, gambling and cryptocurrencies from their partners as part of a pattern of “secret spending”, a new report has found.

More than half of adults in relationships spent in secret on a range of products, according to the research by investment platform AJ Bell and pollster Opinium.

The survey of 4,000 adults showed that men, on average, spent £2,545 without their partner’s knowledge in the past year.

By contrast, women spent an average of £1,769 in secret, the survey found.

The most common secret purchase for men and women was clothing – with it being a purchase for 20% of men and 35% of women.

For women in relationships, beauty products were the next most common, with a quarter saying they had secretly bought them.

Men said their most common secret spend after clothing was on vices such as cigarettes and alcohol, with a fifth (19%) saying they had made the purchases without telling their partner.

Men were also found to be more likely to use their cash for gambling or to send gifts to friends and family without telling their partners.

Gen Z, those born between 1997 and 2012, are more secretive with their spending than older generations, with an average of £4,303 in the past year.

Those over 55, meanwhile, spent an average of just £384 in secret over the same period.

AJ Bell’s personal finance director Laura Suter said a bit of secret spending “might sound harmless” but could potentially highlight “a much bigger issue around how couples manage, discuss and plan their finances”.

She said money being spent in secret could make it “difficult to budget properly or plan for longer-term goals like buying a home, building an emergency pot or saving for retirement”.

Ms Suter warned that gaps between what people say they are spending and what they are actually spending is “likely to be one of the quickest routes to financial friction in a couple”.

She added: “Ultimately, you don’t have to report every time you buy a coffee or get your nails done to your partner, but major costs, recurring habits or anything that risks derailing a joint financial plan should be on the table.”

And finance expert Iona Bain said couples maintaining a degree of financial independence can be “very sensible”.

But Ms Bain warned some partners hide spending from each other “because they have failed to be honest about their values and priorities at an early stage, and they know deep down that their partner wouldn’t approve”.

“This kind of behaviour is understandable but it actually creates more conflict in the long run because it’s impossible to do things like buy a house together or have children without being honest about how you spend your money,” she added.