Brexit negotiations will probably need to run into November to finalise a withdrawal treaty, including a so-called "backstop" agreement to avoid a hard border on the island of Ireland, the Tánaiste has said.

"There is an expectation that the UK side will introduce some legal text which I hope can be helpful," Simon Coveney said.

"Whether or not that can be the basis for a significant step forward between now and the (European) Council meeting next week, we simply don't know yet.

"What we do know is that the talks process has intensified this week on trying to find a way forward on the backstop but I suspect November will probably be needed as well as October to get agreement on that but we'll know an awful lot more next Monday and Tuesday."

Mr Coveney also said that if Britain leaves the European Union without a deal it will lead to economic carnage, particularly for Britain itself.

"If Britain crashes out of the EU without any deal on anything, from aviation to the common fisheries policy to border controls, you are talking about carnage, particularly for Britain. Ireland will still be a member of the European Union and have huge solidarity from member states," he said.

Earlier today DUP leader Arlene Foster repeated her insistence that there should be no customs or regulatory barriers between Great Britain and Northern Ireland, and said she had made this clear to the British Prime Minister Theresa May.

Speaking in the European Parliament following a meeting with the EU's chief negotiator Michel Barnier, Mrs Foster said the Brexit talks were entering a "critical phase".

She told reporters: "There cannot be barriers to trade in the UK internal market. It would damage the economic well being of Northern Ireland. Therefore we could not support any arrangement which would give rise to either customs or regulatory barriers within the UK internal market.

"The Prime Minister understands that position and I expect her to respect that position."

Speaking alongside DUP MEP Diane Dodds, Mrs Foster said she had not yet seen a fresh text on the Irish backstop, a guarantee of no hard border on the island of Ireland, from the British government.

Pressed if the DUP would veto any EU-UK agreement on the backstop, Mrs Foster said she would have to wait to see the detail of any text, and would not comment "in a vacuum".

But she appeared to reinforce the party's red line on checks along the Irish Sea in the event of the backstop taking effect.

"The whole point about checks is that there is a difference" she said. "Why would we need checks between Northern Ireland and GB, or between GB and Northern Ireland, if we were an integral part of the single market of the United Kingdom?"

Mrs Dodds said that Northern Ireland sold more goods to the GB market than the Republic of Ireland, the EU and the rest of the world "combined".

To put up tariff or non-tariff barriers would be "economically disastrous," she said.

She said regulatory checks as part of the backstop could mean Northern Irish milk being processed in England and turned into yoghurt or protein drinks facing checks when they came back into Northern Ireland.

Mrs Foster added: "If there was a border down the Irish Sea then NI would not be able to benefit from any future trade deals that the United Kingdom government would pull together. That's certainly not where I want to be. I want to be part of a 'global UK'."

Mrs Foster and her party have been accused of "not representing" the majority view in Northern Ireland following the meeting.

Sinn Féin's deputy leader Michelle O'Neill said: "The DUP do not speak for the majority of people here on Brexit, just as they do not on a range of social issues, including the rights of women, Irish speakers, victims and the LGBT community."

"I also believe that Arlene Foster's so-called blood red lines are out of step with many in the unionist community who are growing increasingly concerned at the DUP's willingness to endanger our economy in order to avoid an imaginary line on the Irish Sea."

Ms O'Neill, along with the leaders of the SDLP, Alliance Party and Green Party, met with Mr Barnier last week.

"We did so as the majority voice of the people here," she said.

"All those parties made it clear that, in terms of Brexit, the DUP should not have a veto.

"We also re-iterated our common position that the 'backstop' as already agreed must be maintained and is the absolute bottom line for Sinn Féin, SDLP, Alliance and Green Party as we enter the endgame of the Brexit negotiations."

Separately, the Irish Exporters Association has said that exporting companies could see a 23% hit to their cash flow from VAT on imports in the event of a no-deal Brexit.

Chief Executive Simon McKeever said that at present companies importing products, eg components for manufacturing, would have until the 15th of the following month to pay the VAT if importing from an EU member state.

However, if importing from a non-EU country - which Britain would be post-Brexit - companies would have to pay VAT of 23% at the point of entry, and the goods would not be released until the VAT was paid.

Mr McKeever voiced concern that this would hit supply chains into Ireland, as well as cash flow for companies, and could potentially hike costs for consumers.

He called for a six month derogation for companies to pay import VAT in such circumstances.

He said he believed the Government was not preparing for a no-deal Brexit or for a "potential crash-out".

Additional reporting Ingrid Miley