Downing Street has rejected a claim by the former head of the diplomatic service that the Brexit talks have not begun promisingly for the UK.
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 and that it had been "a bit absent" from the negotiations in Brussels.
His comments were rejected by the Prime Minister's official spokesman who said the two rounds of talks which took place between Brexit Secretary David Davis and the EU's chief negotiator Michel Barnier had made important progress.
"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," the spokesman said.
"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."
In an interview with BBC Radio 4's Westminster Hour, Sir Simon, who now advises businesses on Brexit and foreign policy, said: "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."
With the Government expected to publish further "position papers" setting out its views on customs arrangements and the Northern Irish border in the coming weeks, Sir Simon said it would help demonstrate the UK team is "ready to engage".
"I think so far we haven't put much on the table apart from something on the status of nationals, so we are a bit absent from the formal negotiation," he said.
Downing Street also played down weekend press 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.
The EU budget commissioner Guenther Oettinger meanwhile warned that UK payments would have to continue after it left the EU in March 2019 as it would remain "bound" by previous commitments.
"London will therefore have to transfer funds to Brussels at least until 2020," he told Germany's Bild newspaper.
Downing Street said ministers had already accepted that there would be obligations which would "survive" the UK's withdrawal and that these would have to be resolved.