Home Secretary Amber Rudd has dismissed a leak of Brexit talks as "tittle-tattle" amid further reports of concerns in Brussels.
Ms Rudd also said it was a mistake that details of a dinner at Downing Street last week had appeared in the press, with the Government saying it would not enter into a briefing war with the European Union.
The comments came after senior EU sources told the BBC that the UK failed to understand how the bloc works, prompting fresh fears Britain would fail to secure a trade deal after Brexit.
Prime Minister Theresa May has come under fire following reports European Commission president Jean-Claude Juncker walked out of talks last week in Downing Street saying he was "10 times more sceptical than before".
Ms Rudd told ITV's Good Morning Britain she was not at the dinner with Mr Juncker, but said: "We are not going to comment on leaks like this - they may or may not be true, elements of it - but the fact is there is going to be nearly two years of this type of negotiation going on and I think it would be a mistake for the Government to leap on and back on any sort of tittle-tattle that comes out."
The Government position is that "we can be relied on to keep gossip out of the press" so it can get a good deal for the UK, she added.
She later told the Today programme on BBC Radio 4: "I'm not surprised that there is briefing coming out from different sides of a negotiation.
"But what we will always do is make sure that we conduct our negotiations more discreetly, shall we say, so that really we can have a freer negotiating hand.
"I think it's a mistake to allow those sort of details, if they are true, to come out from a dinner."
She said she did not know if the details were true, but said they were in conflict with other views from senior EU commissioners.
Mrs May has dismissed claims she is at loggerheads with Mr Juncker over her Brexit negotiating strategy as just "Brussels gossip".
High-level EU sources have told the BBC that the UK is on "a completely different wavelength" over the negotiations.
They reportedly accused the UK of misunderstanding the talks and how Brussels works, as well as falsely believing the EU's red lines in negotiations could be flexible.
This has fuelled belief in Brussels that talks over a new trade deal could fail, according to the BBC.
According to the account in the German Frankfurter Allgemeine Sonntagszeitung newspaper - attributed to commission sources - the EU side left the meeting believing Mrs May was way too optimistic about the prospects for a deal.
As he left, Mr Juncker was said to have told her: "I leave Downing Street 10 times as sceptical as I was before."
The following morning he rang German Chancellor Angela Merkel to warn her that Mrs May's approach was from a "different galaxy" and that she was deluding herself.
Mrs Merkel responded by rewriting a speech she was giving that day to warn that some in Britain were still harbouring "illusions" about the Brexit process.
No 10 said it did not recognise the account of the meeting, which took place over dinner last Wednesday.
Stephan Mayer, home affairs spokesman for Chancellor Merkel's parliamentary Christian Democrat group, told BBC Radio 4's Today programme: "There is a comprehensive entrant position within the EU27 and one decisive pillar of this position is Brexit means Brexit and if you leave, you leave with all the consequences.
"I'm also convinced that this Brexit isn't in the interest of the European Union, and especially not in the interest of Germany, but the consequences will be worse for the UK.
"If someone in Great Britain thinks that Great Britain will be the winner or takes advantage of this Brexit, I'm convinced this would be an illusion."
Speaking during a campaign visit to Lewes in East Sussex, Liberal Democrat leader Tim Farron said: "Whether you see these as leaks or Brussels gossip, the whirlwind of news following the May-Juncker meeting is a taste of what's to come.
"The reports show a Prime Minister who is complacent and seems to have no idea how difficult these negotiations will be.
"It looks like the Conservatives want to negotiate Brexit in back rooms and over champagne lunches hidden from the scrutiny of Parliament or the public.
"The Liberal Democrats want to trust the people with the final say on the deal, Theresa May wants a stitch-up by politicians and bureaucrats."