Listeners to BBC Radio 4 are two and a half times more likely to hear the opinions of a pro-EU speaker than from anti-EU guests despite Britain’s recent vote to leave the EU, research has found. MPs on both sides of the house written to BBC bosses in protest, saying the figure points to clear bias within the Corporation.

Recent research by think tank News Watch, which analysed a group of 31 Radio 4 programmes and Features re-released by the channel in an i-Player series entitled “The Brexit Collection” found clear indications of bias within the eleven and a half hours of programming.

News Watch’s report noted: “There were no attempts in any programme to explore the benefits of leaving the EU, but conversely, Brexit came under sustained negative attack.

“This was reflected in the balance of contributions and comment contained within the items. Analysis by News-watch shows that only 23 percent of contributors in the programmes as a whole spoke in favour of Brexit, against 58 percent in favour of Remain and 19 percent who gave a neutral or factual commentary.”

Of the programmes, which were originally broadcast over a number of years, the report found that “nine programmes and six features, amounting to 5 hours 20 minutes of programming, were strongly anti-Brexit, contained unchallenged predictions that civil unrest and rioting were now on the horizon and cast the ‘out’ vote in negative terms, inferring that the result had been a consequence of racism and xenophobia.

“The balance of programme guests in all of these items was strongly – and sometimes overwhelmingly – pro-Remain.”

A further eight programs were classed as “neutral”, but included comedy programs such as Dead Ringers and The Now Show which “contained strong anti-Brexit content, or expressed doubts about it,” as well as “some balancing material.”

A group of six documentaries purported to take a critical look at the EU but featured guests who were “wholly in favour of the EU project, or were EU officials”, and as such examined the issues “through a strongly pro-EU lens.”

Within some cultural items, such as Front Row, The Briefing Room, Farming Today, and The Food Programme, researchers noted that “the range of anti-Brexit opinion was astonishing and light years from any definition of ‘impartiality’ and there was no balancing comparable pro-Brexit material.”

Meanwhile, the choice of guests was also illuminating: “across the board, 41 percent of the speakers who supported Leave were ‘ordinary’ contributors (i.e. members of the public with no obvious expertise, for example, in vox pops), compared to only 27 percent of pro-EU guests.”

And of the of the 59 politicians to appear in the programs, 37 were pro-Remain.

A group of MPs have cited the research in a letter, seen by the Daily Mail, addressed to the BBC’s Director General Lord Hall to protest the coverage.

The letter, signed by Conservative MPs Philip Davis and Philip Hollobone, Labour MP Kate Hoey, and the former UKIP leader Lord Pearson among others, notes: “Analysis proves that the BBC is not hosting arguments from the Leave camp, nor is it interrogating Remainers, in anything like a balanced way.

“Your coverage is heavily biased in favour of those who wish to water down or even reverse the referendum decision.”

They added: “Our experience of complaining about individual programmes does not encourage us to try again.

“We complained about Newsnight on the evening of David Cameron’s Bloomberg speech, which fielded 18 Europhiles against one Eurosceptic, and your complaints procedure managed to find that it was a balanced programme. Any new complaints system will not work unless it is independent of the BBC, obviously.

“We are still complaining about your whole editorial line on your post referendum coverage, and we are supported by dozens of News-Watch transcripts.

“We fear these show that the BBC is undermining the Government’s attempt to get a settlement with Brussels which is in accordance with the wishes of a majority of the British people, and in the national interest.”