A household name in the insurance world has set the cat amongst the pigeons by urging consumers to boycott the ever-increasing number of price comparison websites.

The gloves came off this week in the battle between one of the country's best known insurance companies and the price comparison websites that claim to provide consumers with the cheapest motor insurance quotes.

Direct Line - part of the Royal Bank of Scotland group - has launched a major advertising campaign urging consumers to avoid sites such as Moneysupermarket.com and Gocompare.com which, it claims, don't always come up with the best deals.

Using slogans such as 'Price comparison sites may not offer the features you need' and 'Price comparison sites are actually middlemen', Direct Line has gone for the jugular as it tries to convince punters to bypass the comparison sites and buy directly from the insurer.

Direct Line said its research showed that 93pc of people who had used price comparison websites believed they should carry warnings that not all suppliers were included; 41pc of consumers mistakenly believed that such sites quoted all major insurers, with 35pc believing that all insurers were quoted; and only 26pc of consumers were aware that some price comparison websites were affiliated to particular financial groups.

Emma Holyer, a spokesman for Direct Line, said: “Consumers are confused about price comparison websites and our research shows many believe they provide an independent, public service designed to ensure consumers get the best deal on their insurance.

“Unfortunately, this is not the case, as these websites are really just online middlemen who make money out of commissions on insurance sales, just like a traditional high-street broker.

“Direct Line has never sold, and will never sell, its products through middlemen, either online or via high-street brokers, and consumers need to be aware that the only place they can get a quote from us is by coming to us direct.

“In order to put an end to confusion among consumers, Direct Line is calling on price comparison websites to be more upfront about the service they actually provide.”

But the comparison sites have hit back furiously.

“I'm surprised by just how stuck in the past Direct Line now seems,” said Gocompare.com managing director Hayley Parsons.

“Comparison services represent the future when it comes to purchasing insurance. Why would a customer want to enter all their details into individual websites over and over again like Direct Line is suggesting when you can go to Gocompare.com, enter details once and search more than 30 direct insurers and brokers?”

To make its point, Gocompare.com published a list of insurance quotes, comparing its cheapest deals with the equivalent quotes from Direct Line (see chart).

It found that in 90pc of the case studies - examples, it must be emphasised, that were handpicked by Gocompare.com - the Direct Line quotes would not have been the cheapest.

Furthermore, the Direct Line policies would not have included courtesy cars as standard - a point Gocompare.com highlighted in a cheeky stunt this week when it sent a courtesy car to the marketing director of Direct Line.

Confused.com, which is owned by Admiral, has also hit back at Direct Line's advertising campaign, pointing out that RBS is the only major insurance group that has consistently refused to allow consumers to compare its prices on any price comparison site.

“This looks like an act of desperation from an increasingly uncompetitive Direct Line,” said Confused.com managing director Debra Williams.

“It's a shame it won't allow its quotes to be compared through independent price comparison sites.

“But there may be a reason - our initial research suggests that nine times out of 10, Direct Line's quotes wouldn't feature in our top five cheapest prices, and in some cases Direct Line doesn't even make the top 10.”

It's perhaps no surprise that the emotions are running high. Price comparison sites are big business.

Moneysupermarket.com, which has been running its own television campaign recently, was recently said to be worth up to £1bn, while Confused.com has been given a price tag of about £700m.

Kenny Kemp, a director of price comparison site Peopleschampion.com, said Direct Line's claims were “bogus”.

“Direct Line is an excellent company with a wonderful track record of supplying its customers with value-for-money products,” he said.

“But it has been forced to mount a bogus advertising campaign to try to discredit independent price comparison sites.”

It's possible that both sides will see a benefit from this row. Direct Line has earned itself free publicity with its attack on the websites, but the sites themselves are seeing an increase in traffic, with Gocompare.com saying the response to its television advertising campaign had doubled since the argument erupted.

And if all this focuses our attention on making sure we get the most competitive motor insurance quotes, perhaps everyone will be a winner.