Britain plans to use entry points to the Irish Republic as its front line in combating post-Brexit illegal immigration, according to a report.

London wants to beef up controls at the Republic's ports and airports in order to avoid the return of a "hard border" with Northern Ireland, The Guardian reported.

With Britain and Ireland enjoying a common travel area (CTA) since the 1920s, the narrow pro-Brexit vote threw up major problems as any return to a "hard" controlled 300-mile border could be seen to contravene the Good Friday Agreement.

Northern Ireland Secretary James Brokenshire told The Guardian that Ireland's external borders would be strengthened in order to combat unwanted migration once the UK withdraws from the EU.

Mr Brokenshire said there was a "high level of collaboration on a joint programme of work" under way between the two countries to control immigration.

"We have put in place a range of measures to further combat illegal migration working closely with the Irish government. Our focus is to strengthen the external border of the common travel area, building on the strong collaboration with our Irish partners," he said.

"We are already working closely with the Irish government and other members of the common travel area to prevent people from seeking to evade UK immigration controls from entering via another part of the CTA.

"There is a high level of collaboration on a joint programme of work. This includes investment in border procedures; increased data sharing to inform immigration and border security decisions; passenger data systems enabling the collection and processing of advance passenger information; and harmonised visa processes."

Attempts to use Irish entry points such as Dublin Airport and Rosslare port as the front line of British immigration controls could prove highly controversial in the Republic.

The measures will be aimed primarily at non-Europeans seeking entry into the CTA, The Guardian reports, as EU citizens will have automatic rights to enter the Republic.

At present Chinese and Indian visitors apply for a single visa enabling them to visit both Britain and Ireland.