The UK environment secretary, George Eustice, has denied that the departure of Dominic Cummings – one of the architects of Vote Leave – will have any impact on Brexit negotiations. As the Brexit deal deadline approaches, Eustice sought to downplay Cummings’ exit from No 10 by arguing it would not alter discussions with Brussels as UK negotiations are led by David Frost. Downing Street was rocked last week by the departures of Boris Johnson’s most senior aide and his director of communications, Lee Cain, another veteran of Vote Leave, who lost out in a power struggle involving Boris Johnson’s fiancee Carrie Symonds. With Brexit talks due to resume this week before an EU summit on Thursday, viewed in Brussels as a deadline for a draft deal, Eustice was questioned on whether it was easier to get a trade agreement with the EU without Cummings. Eustice told Sky News’s Sophy Ridge on Sunday: “The negotiations have been led by David Frost from the beginning. He’s got a very talented, experienced team of technical experts around him. “He’s led these negotiations from the start and obviously remains in place and continues to do so. So I don’t actually think the departure of Dominic Cummings makes any particular impact on the negotiations, since Lord Frost has been leading those.” Amid reports of counter-briefings between warring factions in No 10, Eustice was pressed on whether the prime minister needed to take responsibility for his staff “tearing strips off each other”. Eustice said: “I’ve known Dominic Cummings myself for many years. He’s got many great strengths and one of them is winning campaigns. And he tends to apply himself in short bursts, short tours of duty, on big strategic changes such as the 2016 referendum result, such as the 2019 general election. “And he’s very talented at that. But look, it’s always the prime minister’s prerogative who will be their key advisers. The prime minister has to have a team around him that he’s comfortable with, that works well to get the right balance. And it’s always the case the prime ministers can change their advisers and change the mix of their advisers.” The former Labour prime minister Gordon Brown painted a complex picture of splits within the Conservative party. “Well, you’ve got 27,000 new [Covid] cases yesterday, 500 deaths, you’ve got a million young people looking for work, you’ve got people without savings planning for Christmas,” he told the BBC’s The Andrew Marr Show. “Really, we should not be in this factional fighting at the moment. And I see no end to this factional fighting because you’ve got a soft Brexit faction, a hard Brexit faction, you’ve got a libertarian faction in relation to health restrictions, a communitarian faction, you’ve got a northern faction wanting spending rising, a southern faction wanting spending cuts, you’ve got a devolution faction and a centralisation faction. “This is not simply a problem of a dysfunctional Downing Street, this is a dysfunctional UK and we really will need a wholesale root-and-branch constitutional review to bring people together at a later stage.” Asked if he thought the departure of Cummings would have any effect on how the government dealt with trade talks, Brown said: “I think the arrival of Joe Biden has made all the difference. “I see a trade deal coming pretty soon. The government simply cannot afford to be at war with America on the one hand and Europe on the other at the start of the new year. So if he [Johnson] doesn’t change his internal market bill he’s at war with America, if he doesn’t get a negotiation settled with Europe he’s at war with Europe. I think he’s made up his mind already that he’s going to get a settlement and there will be a settlement soon, I think.”