The move comes after its research highlighted the importance the sites play in helping consumers make financial decisions. A poll commissioned from YouGov to support the research showed that 45% of people have used a comparison site to help them make a financial decision in the last year.

The research also showed that many sites don’t explain the commercial relationships they have with product providers and fail to explain technical terms and jargon.

The plea has been backed by financial education charity the ifs School of Finance and a number of comparison sites.

Clive Cowdery, chairman of the Resolution foundation, said: “Comparison sites are valuable in making informed financial decisions, but many sites are undermined by a lack of transparency about their commercial relationships. A voluntary code of practice would address this and encourage a growing market, without the need for further regulation.”