Mr Nuttall’s party will demand an instant repeal of the European Communities Act 1972 which would cancel out the need for a lengthy formal departure process.
And he sharply criticised Theresa May’s decision to wait until the end of March to begin two years of negotiations with European Union officials.
Mr Nuttall, who was named as party leader on Monday, wasted no time in giving the job of Brexit spokesman to one of Ukip’s founding fathers Gerard Batten.
Mr Batten, an expert on the technicalities of EU exit, said he would use his new role to show how Britain could get out as quickly and cleanly as possible.
Mr Batten said: “UKIP’s policy will be to reject Article 50.
“We will call for parliament to repeal the European Communities Act 1972 immediately as the first step in the process.”
He continued: “This will restore lawmaking supremacy to the UK parliament and put the British government in the driving seat of negotiations, not the EU.
“We don’t want a ‘hard’ or ‘soft’ Brexit but a democratic and speedy exit. The result of the referendum must be respected and enacted without delay.
“Theresa May and her Tory Government cannot be trusted to deliver our withdrawal from the EU. She was a Remainer who heads a predominantly remain government.
“If she were genuine about delivering Brexit she would have triggered Article 50 the moment she became prime minister.
“Instead nothing has been done in the last five months, and there are no plans for the next four. Then we will face at least another two years of protracted negotiations. Under article 50 they could be extended for years to come.”
He accused Mrs May of trying to “delay and delay the whole process in order to fudge it and to try and foist on us a ‘Norwegian or Swiss’ type EU model whereby we continue to pay money to the EU, obey a large percentage of its laws, and have open borders”.