Online price comparison services, already on the radar screen of regulators, are preparing to launch a code of practice – but without the backing of some of the most popular websites.

The Comparison Consortium, a trade body launched in February this year by a former Moneysupermarket.com executive, next month plans to unveil its code for online insurance aggregators and professional guidance for insurers who use them.

The consortium has also created an accreditation scheme for members to bring an “unprecedented element of regulation and professional standards to the industry as a whole”.

The consortium has the support of the Association of British Insurers (ABI) for its initiatives which come as the sector – often accused of being too price-focused – examines ways to address regulatory concerns about treating customers fairly.

But the code has been drawn up without the input of some of the industry’s biggest players.

“We have never actually been formally asked to join [the consortium],” said Ian Williams at Moneysupermarket.com, the UK’s leading finance comparison website, which said it attracted about 120m visitors and recorded about 900m page impressions last year.

GoCompare.com, which generates more than 1m car insurance quotes a month, said: “We have not had much contact from the consortium. We have not been consulted on this [the code].”

The consortium was set up by Richard Mason, a founder of Moneysupermarket.com, who is now managing director of Moneyextra.com, a smaller rival website.

In spite of these high-profile omissions, the consortium’s committee maintained that it represented the “interests of the entire comparison industry”.

“The Comparison Consortium’s committee. . . collectively has over 45 years experience in the price comparison industry, acquired from the UK’s biggest aggregators, Moneysupermarket, Confused, uSwitch, Moneyextra, Tesco Compare, Beat That Quote and Moneyexpert,” said Jennifer Rose, a spokeswoman for the consortium.

“They are the aggregator elite, the industry pioneers, the ones that been around the longest and are the most active, she added.”

The consortium said it had received requests from a “number of high-profile aggregators who are keen to be awarded the consortium’s accreditation”.

While welcoming efforts to raise professional standards with the new code, consumer groups said its effectiveness would be weakened if the bigger players were not signed up. “It could be argued that the code will struggle to have the impact it wants without the involvement of websites which have the greatest impact on consumers,” said Dan Moore of Which?, the consumer group.

In a separate development, other sector players, including insurers, brokers, consumer groups and some price comparison websites, including Moneysupermarket.com, met this week to discuss how to get the sector working more closely to address concerns over transparency and clarity.

The online price comparison sector is under pressure to clean up misleading practices, such as the use of default insurance policy excesses – as high as £500 on vehicle cover – that can distort quotes. Using assumptions that are not clearly signposted, such as the applicant being the main driver of a car, makes quotes faster at the expense of accuracy.

The ABI, which hosted the meeting, not attended by the Comparison Consortium, is now drawing up an action plan.

The launch of the code comes as insurance comparison aggregators – which have seen their numbers swell from 17 a few years ago to more than 40 – are seeking ways to distinguish themselves in a saturated market.

“In the next five years, we will see the comparison site market contract and there will only be a few ‘super aggregators’ who survive,” said Mike Powell, insurance consultant at Defaqto, the market analysts.