The press briefing at 10 Downing Street comes a day after Mr Johnson resigned as Conservative leader, saying he would step down as prime minister when a Tory leader was found.

This is not likely to be for several months, though Mr Johnson promised he would not use his remaining time as prime minister to make "major changes of direction".

In this light the spokesperson said the Rwanda asylum policy, announced by the government in April, would continue.

It intends to take some asylum seekers who cross the Channel to the UK on a one-way ticket to Rwanda to claim asylum there instead.

So far no-one has been sent to Rwanda from the UK. A flight that was due to take asylum seekers was cancelled before take-off last month, following a last-minute intervention by the European Court of Human Rights (ECHR).

The High Court in the UK is due to hear a judicial review challenging the legality of the deportation policy this month.

"Convention doesn't prevent or preclude government from seeking to fulfil that policy and that would include defending cases in court as required," PA News quotes the spokesperson as saying.

It was possible flights could depart before a judicial review, the spokesperson added.