A hard border between Northern Ireland and the Republic is inevitable after Brexit, MPs have warned.

The Commons Exiting the EU Committee said on Thursday it is impossible to reconcile withdrawal from the single market and the customs union with the government's desire to keep a "frictionless" border.

"We do not currently see how it will be possible to reconcile there being no border with the Government's policy of leaving the single market and the customs union, which will inevitably make the border between Northern Ireland and the Republic of Ireland the EU's customs border with the UK," the committee said.

However, the report split the committee. Four of the eight Conservatives present as well as the lone Democratic Unionist voted against it.

The Irish government has repeatedly raised concerns over the issue, and has demanded written guarantees from Westminster there will be no return to the border checks of the past after Britain leaves the EU.

Premier Leo Varadkar said without such assurances, EU leaders will not proceed to the second phase of the Brexit negotiations, specifically talks around a free trade deal, which are scheduled to begin in mid-December.

The committee’s report urged the Government to begin work on ensuring goods continue to flow in and out of the UK as freely as possible, including the installation of electronic customs checks and the construction of a lorry park at the Port of Dover.

"Such measures would not deal with all the risks of serious delays in Dover and would have to be reciprocated across the Channel in order to be effective," the committee warned.

Craig Mackinlay, one the four Tory Brexiteers who voted against the report, argued that leaving the single market and the customs union does not mean a "physical border" would be necessary between the North and the Republic.

"Of course, there has long been a VAT and currency border. Goods and services entailing cross-border transactions have paperwork and electronic filing to efficiently and effectively handle the different tax regimes," he said.

"If we end up with the World Trade Organisation model, for instance, I see no reason why it is not possible to add a customs tariff, if necessary under a no deal scenario."