Phone and broadband bills are the biggest source of unpleasant surprise for householders, research has found.

Billpayers on average shelled out almost 60 per cent more than they had expected, or an extra £1459 on top of expected annual outgoings of £2528, according to Santander.

But by far the nastiest bill was phone and broadband, at a typical £1100, more than double the expected £514.

The research coincides with a campaign by the Advertising Standards Authority to clamp down on misleading broadband advertisements.

Citizens Advice published research last year showing customers can pay up to six-and-a-half times more a month for broadband than the headline rates in promotions.

Gillian Guy, chief executive of Citizens Advice, said customers were being promised one thing, and charged for another.

“Burying the cost of line rental in the small print of adverts or not properly explaining the duration of a contract are blatant attempts to mislead people. It is confusing and makes it difficult for consumers to know how much they’ll be charged or to compare deals from across the market.”

She added: “If the ASA can get broadband providers to advertise all-inclusive up-front costs and make contract lengths clear it will help consumers make informed choices.”

Robert McKechnie, managing director of Edinburgh-based telecoms challenger TenTel, said the ASA and Ofcom research into how broadband packages are marketed showed that four out of five people were unable to identify correctly the total cost per month of a broadband contract after viewing an advert for broadband services.

He said: “We absolutely welcome the decision by the ASA and Ofcom to change the way broadband services are marketed to the public. Anything that leads to greater transparency and competition among suppliers is good for customers.

“Clearly, consumers are struggling to understand what they are signing up for, or for how long, and can get trapped in long-term contracts or find themselves paying for extras that they just don’t want. This can be devastating for those on a tight budget and disproportionately hits groups who need short-term contracts such as students and rental tenants.”

Ofcom is also planning new rules to let broadband customers exit contracts more easily.

Companies including BT, EE, Sky and TalkTalk will be told they have to let customers walk away from their contracts without paying onerous penalties if they don't deliver what they promised.

Citizens Advice says telecoms firms can charge up to £800 for customers if they want to end their contracts early, even when they complain of a poor signal.

The charity received 21,500 complaints about mobile phone problems in 2014.

According to a cross-party group of 121 MPs, broadband customers can ensure “dire” internet connections at home and at work and the situation is “untenable”. Some customers could wait up to two hours to download an hour-long video, and businesses in the worst-affected parts of the country had even been forced to close, the report said.

But prices have continued to shoot up. Households are paying £1000 a year for deals which cost them £750 only four years ago, according to an analysis by comparison site Simplify Digital. It estimates that the big four providers - BT, Sky, TalkTalk and Virgin -- have hiked prices on 90 separate occasions in four years.

Comparison site broadbandchoices.co.uk, which has Ofcom approval, said yesterday: "Many consumers stick with the provider they already have for fear of making the wrong decision and then being tied into a lengthy contract. But by not switching providers regularly, they may be paying considerably more each month than they need to. It is possible they could be paying the same rate for broadband that they originally agreed to as well as the current, elevated line rental price.

"By comparing packages from all of the major providers and switching a person could save over £317 a year. For this reason it is wise to compare providers annually and certainly at the end of a contract."

Mr McKechnie said: “Consumers deserve better, clearer options and they should be able to trust that their broadband provider is not going to rip them off. Our pricing model challenges what we have come to expect as the norm from the big players in the industry.

“From day one we have offered an all-in pricing option, with our Advance bundle, so our customers can see exactly how much they are paying for before they sign up. We also offer a ‘no contract’ option for people who need more flexibility, and we promise flexible, transparent telecoms options which focus on customers’ needs.”

www.broadbandchoices.co.uk