Reform UK leader Nigel Farage has shifted on his pledge to stop migrants arriving on small boats within two weeks of entering government if they win power.

Farage told the BBC’s Sunday with Laura Kuenssberg programme that he would stop the boats within two weeks of passing laws that he says would allow him to deport migrants quickly.

When asked if passing those laws could take months, Farage said a government led by him would “want to do it as quickly as we possibly can”.

The two week pledge was one of the standout announcements of Farage’s keynote speech to his party’s conference in Birmingham on Friday.

He told activists: “In his conference speech on Friday, Farage said: “We will stop the boats and we will detain and deport those who illegally break into our country doing what nearly every normal country around the rest of the world does.

“You cannot come here illegally and stay we will stop the boat within two weeks of winning government.”

In plans announced last month, Reform UK suggested it would be prepared to deport 600,000 migrants over five years if it won power at the next general election.

Farage said his party would bar anyone who came to the UK on a small boat from claiming asylum and make £2bn available to offer payments or aid to countries like Afghanistan to take back migrants.

Key to the plan is the passage of a new law called the Illegal Migration (Mass Deportation) Bill.

Reform UK said the bill would create a legal duty for the home secretary to remove illegal migrants, and ban anyone who had been deported from re-entering the UK for life.

The bill would also “disapply” international treaties like the Refugee Convention, a 1951 treaty that prevents signatory countries like the UK from returning refugees to countries where they face serious threats to their life or freedom.

When asked how that would work, given the complexities and typical timelines of passing legislation, Farage told Laura Kuenssberg: “As soon as the law is in place. As soon as you have the ability to detain and deport, you’ll stop it in two weeks.”

Citing Australian policies, Farage said once the country had “the legal base” to tow small boats back to Indonesia they solved the problem in two weeks.

Under former Australian Prime Minister Tony Abbott’s offshore detention policy, asylum-seeker vessels were controversially turned back to Indonesia and would-be refugees sent to Papua New Guinea and Nauru in the Pacific for processing and resettlement.

In June 2014, Abbott said Australia had marked six months since the last asylum-seeker boat arrival in December 2013 – a few months after he took office.

When Farage was asked if he was making promises he could not keep, he said he meant what he said about mass deportations.

He accused other political parties of telling “the electorate what they think the electorate want to hear without every intending to deliver it”.

Watch the full interview with Farage on Sunday with Laura Kuenssberg at 0900 BST on BBC One and on BBC Iplayer.