Reform UK have pledged to build dozens of immigration detention centres in constituencies that vote Green.

In a provocative move, Zia Yusuf said facilities designed to hold 24,000 people would be placed in areas where the public had backed a party committed to 'a world without borders'. 

Under plans for a new 'Mass Deportation Act', local authorities would lose the power to block unwanted facilities, leaving local residents with few options but to accept the new centres.

Reform has committed to deporting up to one million foreign nationals over five years if it gains power at the next election.

Those identified for removal will be offered a plane ticket and £1,000 in cash to help them make a fresh start in their home country.

Those who refuse will be detained for removal.

Reform said the plan would require the ability to detain up to 24,000 people at any one time – almost ten times the capacity of existing immigration removal centres.

Mr Yusuf, Reform's home affairs spokesman, said it was 'fair' to build the facilities in areas that had shown an enthusiasm for an open borders immigration policy.

He offered a guarantee that none would be built in constituencies that return Reform MPs and councils. 

'Reform UK has committed to deporting all illegal migrants in Britain, a policy the majority of British people support,' Mr Yusuf said.

'In order to do so, we will need to detain migrants while they await deportation. Even though illegal migrants will not be allowed to leave the sites, we are committing to not placing these detention sites in areas with a Reform MP or where Reform controls the council.

'Given the Green Party advocate for open borders and for an infinite number of undocumented men to come here, we will prioritise Green constituencies and Green controlled councils to locate these detention centres. This is the fairest approach to ensuring democratic consent for all aspects of our mass deportation programme.'

Nigel Farage has pledged a Reform government would stop the boats within months of taking office. But he has also committed to a major deportation programme that could see the removal of huge numbers of people who have arrived in recent years.

Up to 400,000 people granted asylum could have their status revoked if they are found to have arrived in the UK illegally, claimed refugee status after overstaying their visa or arrived from countries that are now considered safe.

The Green Party's 'world without borders' policy suggests an amnesty for asylum seekers whose claims have been rejected and calls for a 'fair and humane system of managed immigration where people can move if they wish to do so'.

It says that immigration should not be treated as a criminal offence 'under any circumstances' and suggests that new arrivals should be treated as 'citizens in waiting'.

Immigration removal centres, such as Yarl's Wood, in Bedfordshire, have often proved controversial with local communities. 

Reform's Mass Deportation (Detention) Act would give ministers 'absolute discretion' over the siting of new detention centres, sweeping away a series of current laws and offering no legal right to appeal.

The party has also pledged to scrap a series of human rights commitments to speed up removals, including ending the UK's membership of the European Convention on Human Rights (ECHR).