Image caption Michel Barnier said his "door is open" to Arlene Foster and the DUP

The EU's chief Brexit negotiator has denied Arlene Foster's claims that he has been "aggressive" towards Northern Ireland unionists in the Brexit talks.

It comes after the DUP leader said Michel Barnier did not understand the dispute and was not an "honest broker".

Mr Barnier said he was not ready to engage in "polemics" with Mrs Foster.

Monday marks the start of his Michel Barnier's two-day visit to Ireland, which comes amid rising tensions over the future UK-Ireland border.

He told a press conference in Dundalk at the beginning of the all-island Brexit forum that his "door is open" to Arlene Foster and the DUP.

He said he had not approached the negotiations in a "spirit of revenge".

Media playback is unsupported on your device Media caption DUP leader Arlene Foster: Brexit negotiations have 'become aggressive'

He added that he regretted Brexit and said he was determined to work with the UK to find a solution to the Irish border issue.

The all-island Brexit forum is being hosted by the Taoiseach Leo Varadkar and his deputy, Simon Coveney.

On Sunday Mr Barnier said the UK was contradicting itself over its Irish border policy.

But Mrs Foster said she believes Mr Barnier does not understand the dispute and is "not an honest broker".

In return he said that Mrs Foster needed to respect that his role was to negotiate on behalf of the EU and not to act as a mediator.

Meanwhile the Taoiseach (Irish prime minister) again said that there needs to be "meaningful progress" on border issue by the June EU summit.

Leo Varadkar said otherwise it will be difficult to get the Withdrawal Agreement in place by October.

Image caption The two-day all-island Brexit forum began on Monday

In December, the UK and EU reached a political agreement in which the UK committed to protecting north-south cooperation on the island of Ireland.

It also guaranteed there would be no hard border, including physical infrastructure or related checks and controls.

However, the EU's proposed backstop solution to avoid a hard border - keeping Northern Ireland in the customs union after Brexit - continues to be at odds with what the UK government and the DUP say they would accept.

Mrs Foster told BBC political editor Laura Kuenssberg the DUP would not accept Northern Ireland being treated differently to the rest of the UK.

Image copyright Reuters Image caption Arlene Foster has warned Michel Barnier the DUP will not accept Northern Ireland being treated differently to the rest of the UK

She said: "Michel Barnier's trying to present himself as someone who cares deeply about Northern Ireland and if that is the case he needs to hear the fact that we are part of the United Kingdom [and] will remain part of the United Kingdom constitutionally, politically and economically.

"Therefore his proposal of us being in an all-Ireland regulatory scenario with a border down the Irish Sea simply does not work.

"It does not work constitutionally, politically and it certainly does not work from an economic perspective."

Media playback is unsupported on your device Media caption The Irish border bridge where stakes are high

Mrs Foster added: "We've tried to get him to understand the unionist position for the people of Northern Ireland but he hasn't really responded and I'm disappointed about that.

"I don't think he does understand the wider unionist culture of Northern Ireland."

The DUP are also expressing annoyance that Taoiseach (Irish prime minister) Leo Varadkar is visiting Northern Ireland later without giving notice.

Mr Barnier is due to meet Mr Varadkar on Monday and will also speak to business leaders on both sides of the Irish border during his trip.