Huw Edwards has defended the BBC’s journalism against claims of bias, warning that “toxic cynicism” about the broadcaster’s news output during the general election risks undermining the corporation as it comes under attack from the new Conservative government.

The host of the BBC’s election night coverage said journalists had been under enormous stress in recent weeks as a result of criticism from all sides of the political divide. He said the alternative was “the kind of dross that’s polluted American political discourse”.

“Providing a fair and balanced account of a complex election campaign – with feelings running high on all sides – is difficult enough. Trying to do so while dealing with relentlessly vitriolic attacks is doubly challenging,” Edwards said.

“And you realise yet again that the real purpose of many of the attacks is to undermine trust in institutions which have been sources of stability over many decades. The apparent purpose, in short, is to cause chaos and confusion.”

Downing Street confirmed on Monday that the culture secretary, Nicky Morgan, who stepped down as an MP at the election citing the impact of the role on her family, had been elevated to a peerage and would retain her ministerial job.

The surprise reappointment may be only temporary until a wider post-Brexit reshuffle planned in January. Over the weekend a wide range of candidates to replace Morgan had been mooted, including the former culture secretary John Whittingdale and the newly elected Andrew Griffith, a former senior Sky executive.

Downing Street has already said it intends to look at decriminalising non-payment of the TV licence fee which funds the BBC, potentially downgrading it to a civil offence, similar to non-payment of a utility bill.

When the government looked at the issue five years ago, an independent review concluded that the current system should be maintained as decriminalisation would put at risk around £200m of BBC revenue.

The review concluded that maintaining non-payment as a criminal offence was “broadly fair and proportionate response to the problem of licence fee evasion and provides good value for money” while the licence fee funding model remained intact.

In addition to criticism from the Conservatives, the BBC has come under attack from the left. On Monday Andy McDonald, a member of the shadow cabinet, claimed the BBC had “played a part” in Labour’s election defeat.

Play Video Shadow minister criticises BBC after Labour's election defeat – video

“We’ve always had the print media, which is page after page after page of press barons absolutely destroying and vilifying Labour leaders from time immemorial. What’s changed in this election is the way the broadcast media have joined in with that battle,” he told BBC Radio 4’s Today programme.

“If the BBC are going to hold themselves out as somehow having conducted themselves in an impartial manner, I think they’ve really got to have a look in the mirror.”

YouGov polling released on Monday suggested the proportion of the population who did not trust the BBC’s news journalists to tell the truth rose from 14% to 20% during the election campaign.

Channel 4 also faced criticism from the Conservatives during the campaign. There continues to be speculation about whether the government would consider changes to broadcasting legislation that would allow for more opinionated news coverage on British broadcast channels. It could be possible to force this through the House of Commons, where the government has a large majority, but it could face opposition in the Lords because no such policy was mentioned in the Conservative manifesto.

Edwards, who has worked at the BBC for 35 years, said mistakes made during the campaign were human errors. “The most curious notion of all (promoted with great energy by the BBC’s critics on both left and right) is that these mistakes are often deliberate,” he said, “carefully planned to undermine one party and boost another. These critics imagine a world in which thousands of BBC journalists – of all backgrounds, nationalities, outlooks – work to a specific political agenda dictated by a few powerful individuals, as one commentator insisted recently on social media.”

He said this would not work at the corporation. “BBC News is a rather unsettling mix of awkward, contrary and assertive people who (in my very long experience) delight in either ignoring the suggestions of managers or simply telling them where to get off.”