Northern Ireland’s unfettered access to the Great Britain trade market is “absolutely paramount”, the Secretary of State said.

Physical customs posts are set to be funded at the country’s ports ahead of the UK’s exit from the EU, a Stormont committee has been told.

Brandon Lewis told MPs he was determined there would not be a border down the Irish Sea.

He said: “We want to make sure there is unfettered access for Northern Ireland.

“Northern Ireland is part of the UK’s single market, it is important it remains that way, it is important that we trade both ways.”

Northern Ireland is set to continue to follow EU single market rules on agricultural and manufactured goods after Brexit, while the rest of the UK has the ability to diverge from the end of this year.

Northern Ireland has a busy harbour and two airports in Belfast.

Larne port in Co Antrim also carries a significant amount of freight to and from Cairnryan in Scotland.

They could all see control posts under the British Government’s plans as part of the Brexit agreement.

Mr Lewis told the Northern Ireland Affairs Committee: “We are determined there will not be a border down the Irish Sea.

“The best way to achieve that is to have as close to unfettered access both ways as we can possibly get, certainly unfettered access for Northern Ireland to Great Britain is absolutely paramount and key for us.”

According to the Northern Ireland Statistics and Research Agency (NISRA), Northern Ireland’s sales to Great Britain fell by £1.1 billion (9.3%) over the year to £10.6 billion during 2018.

Great Britain remained the “most significant single market” for external sales from Northern Ireland businesses, accounting for 15.4% of total sales, the NISRA report said.

The coronavirus pandemic has crippled many businesses in Northern Ireland, including those transporting goods between the country and the rest of the UK.

North Antrim MP Ian Paisley said lorries were returning to Northern Ireland empty after delivering goods to Great Britain as the economy remains largely in deep freeze.

He said: “It will result in a lot of our businesses being put in jeopardy.”

The Democratic Unionist said any Government rescue package should cover all sizes of freight vehicles, not just smaller ones.

Mr Lewis said: “We are consistently reviewing the situation.”

Northern Ireland’s exports to the Republic of Ireland increased by £330 million (8.6%) over the year to £4.2 billion during 2018, equating to 6% of all sales.

My anxiety is that there is data being gathered but it is also metaphorically gathering dust somewhere as well

Committee chairman Simon Hoare said there should be more data on the rate of coronavirus infection close to the Irish border as policymakers decide how best to kickstart the economy.

He said: “My anxiety is that there is data being gathered but it is also metaphorically gathering dust somewhere as well.”

Mr Hoare said that would help inform whether Northern Ireland should follow the UK approach or adopt an all-island policy for exiting the restrictions.

He said: “It does not take a biochemical genius to consider that the process would end, that the lockdown approach would need to evolve and look at whether there are flashpoints and hot spots and whether there are greater numbers along the border.”