- Video report by ITV News Political Correspondent Carl Dinnen
Downing Street has rejected a claim by the former head of the diplomatic service that Brexit talks have not "begun particularly promisingly".
Sir Simon Fraser, who was the chief mandarin at the Foreign Office until 2015, said Cabinet divisions made it hard for the government to establish a clear position.
In response, the Prime Minister's official spokesman said: "We would disagree strongly (with Sir Simon's comments). The last two months, we have had a constructive start to the negotiations. We have covered a significant amount of important ground.
"As the Secretary of State for Exiting the European Union said at the end of the last negotiating round, important progress has been made in understanding one another's positions on key issues."
The intervention came after Sir Simon, who now advises businesses on Brexit and foreign policy told the BBC: "The negotiations have only just begun, I don't think they have begun particularly promisingly, frankly, on the British side.
"We haven't put forward a lot because, as we know, there are differences within the Cabinet about the sort of Brexit that we are heading for and until those differences are further resolved I think it's very difficult for us to have a clear position."
- How have Brexit talks gone so far?
Brexit Secretary David Davis and the EU's chief negotiator Michel Barnier held two rounds of talks over June and July.
Davis vowed to make "real progress" ahead of last month's discussions over key issues such as citizens' rights, separation issues and Northern Ireland.
However in a news conference following the second set of four-day talks, Mr Barnier said the UK and Brussels have "fundamental" disagreements over citizens' rights.
Mr Davis described initial Brexit talks as "robust but constructive".
- Row over Brexit divorce bill
Downing Street also played down weekend reports that the government was ready to pay a £36 billion "divorce bill" to the EU in order to secure a free trade deal with the bloc after Brexit, following an angry response from some Tory MPs.
The Prime Minister's spokesman said that while the UK had always accepted there would have to be a "fair settlement" in respect of the UK's outstanding liabilities, they did not recognise the reported figure.
"The Prime Minister made clear in the letter triggering Article 50 that the UK and the EU need to discuss a fair settlement of both our rights and our obligations as an EU member state, but in terms of this figure I don't recognise it," the spokesman said.
Last month Foreign Secretary Boris Johnson suggested European leaders can "go whistle" if they expect Britain to pay a divorce bill following withdrawal from the EU.