It used to be easy covering election campaigns. As soon as the battle began, the stopwatch came out and it was equal airtime for the Tories and Labour – with a scaled down amount for the Liberal Democrats. In the 1980s, when I started working in network radio, it was standard practice to feature only the two main parties on many of the big issues. Balance was simple.

Now, fragmentation is the order of the day. In the past decades we have witnessed the surge of the nationalists in Scotland and Wales; then Ukip and the Greens first won seats in the European Parliament in 1999; and, if elections to Strasbourg happen on 23 May, the parliament may feature members of the Brexit Party and Change UK. Whatever the pros and cons for the country of a multiparty system, it is a nightmare for the broadcast news organisations. They have a long list of politicians clamouring for airtime; and in a round-up package on a day’s campaigning there could be nine leaders with a plausible case for their voice to be heard. That is leaving aside Northern Ireland, where the different party line-up means it has to be treated separately unless you want the number of participants to run into double figures. Even the most skilled production teams cannot make much sense in a report when they have to cram in half-a-dozen or more conflicting soundbites, and the inevitable result is compression, meaninglessness and frustration for all involved.

This struggle is informed by a genuine wish to be fair at these crucial times for a democracy. The broadcasting regulator Ofcom, charged with policing election coverage, formally abandoned the concept of “larger parties” when it amended the rules for campaign output in 2017. “Broadcasters will have greater editorial freedom,” it proclaimed, thus cheerily handing over a parcel that was making a loud ticking noise. There is continuing guidance, though, with Ofcom recently producing documents on the 2019 local and European elections. The key clause in deciding the balance of election-related programming is that it places more weight “on evidence of past electoral support than evidence of current support (eg opinion polls)”.

This is a long-established policy that seeks to anchor coverage around the parties that can prove they have won votes rather than simply capturing the mood of the moment. It was used to keep the SDP in perspective when it hit 50 per cent in the opinion polls after its launch in 1981, and similarly the zenith of Nick Clegg during the 2010 election campaign.

But 2019 will prove the broadcasters’ toughest challenge yet, and not just in allocating airtime to Change UK – which has no past electoral support except for 11 MPs voted into the Commons for other parties. Even more acute is the question of Ukip and the Brexit Party. Ukip won the European elections in 2014 (the overall turnout was 35.6 per cent), but several MEPs have defected to the new Farage grouping and predictions are that the Brexit Party will sweep Ukip aside. Yet the guidance would appear to prioritise Ukip. In terms of party election broadcasts (PEBs) – those five-minute TV advertisements – another criterion is being used: whether parties are fielding a full slate of candidates across a nation. This means that the Brexit Party and Change UK are among seven parties that will get PEBs in England on the main channels.

What is striking, though, is the hostility vented on social media about the principle that every legal political party should have its right to the public airwaves. Just look at the uproar every time the BBC puts Nigel Farage on air. In his tour de force performance on The Andrew Marr Show last month, the Labour MP David Lammy went further in condemning the corporation for allowing “extreme hard-right fascism to flourish” with the examples cited including Jacob Rees-Mogg and Boris Johnson, who are elected members of the governing party. My former BBC colleague Paul Mason wrote in the New Statesman that “on programmes such as Question Time, Good Morning Britain and the new breed of overtly partisan talk radio stations, totalitarian ideas are being normalised”. (The Ukip leader, Gerard Batten, was a guest on the same Marr show on which David Lammy appeared.)

Their concern is understandable, but the principles of democracy and public media are at stake too. The logic of many of these arguments would ban some views from the airwaves, in the way the Thatcher government banned Sinn Féin. It was both anti-democratic and counterproductive, though the alternative has risks too. I was a member of the BBC journalism board ten years ago when the decision was made to put the BNP’s Nick Griffin on Question Time because he was an MEP, and I still believe it was the right thing to do. Griffin and the BNP shrivelled under scrutiny. In the same way, it seems preferable to have Gerard Batten and his ghastly entourage exposed, as Kate McCann from Sky News did recently, prompting him to walk out of the interview.

Yet it is essential that free speech, and the right of people standing for election to have their voice heard, are accompanied by the sort of scrutiny that public broadcasting can offer. There are editorial lapses: for years Boris Johnson was often portrayed as an engaging comedy act, with the unforgivable contraction of his name to “Boris”. Farage has also been overindulged as a media personality. Question Time has been right in its commitment to airtime for all, but wrong in not subjecting participants to tougher, expert analysis of their policies. And that is now the question facing the whole of the media: do they lock some people in a dark cupboard and hope they’ll never be heard from again, or expose them to the light?

Roger Mosey is the master of Selwyn College, Cambridge, and a former head of BBC Television news