Image copyright PA Image caption UKIP says fishing rights will be a key litmus test of a Brexit deal

The UK must have "full control" of its borders and territorial waters after Brexit, UKIP has said as it set out six tests for Theresa May as she prepares to begin the process of leaving the EU.

UKIP wants full "maritime sovereignty" and Parliamentary supremacy over laws, no "divorce bill" nor payments to the EU budget after the UK's withdrawal.

Party leader Paul Nuttall said UKIP would act as the "guard dog" of Brexit.

The prime minister will invoke Article 50 on Wednesday.

This will trigger a two-year process in which the UK and the remaining 27 EU nations will seek to agree the terms of the UK's exit as well as the outline of the UK's future relationship with the union.

In a speech on Monday, Mr Nuttall said that the UK's exit - set in motion by last year's Leave referendum vote - must be "done and dusted" by the end of 2019.

As it stands, the UK is on course to leave the EU on 29 March 2019, unless both sides agree to extend talks. But Brexit supporters have also spoken for the need for a completely "clean break", arguing there can be no transitional arrangements nor payments to maintain access to the single market afterwards.

Mr Nuttall set out six key objectives that he says any acceptable final agreement must be judged against:

Full control of immigration, asylum and border controls

Restoration of full maritime sovereignty

A seat on the WTO with the UK free to do trade deals with whoever it likes

No final settlement payment and no ongoing payments to the EU budget

No impediments nor restrictions on the law-making supremacy of UK Parliament

Brexit must be over by the end of 2019

"While we will be willing Mrs May to succeed in agreeing to a full Brexit on our terms, we want her to keep faith with the will of the British people as expressed in the referendum result," he said.

"We will also be letting her know that the political price she will pay for backsliding or watering down the ambitions will be very high indeed. I have described this role as akin to being the guard dog of Brexit."

UKIP has suggested fishing will be one of the early tests of how hard a bargain Mrs May is prepared to drive.

Image copyright UKIP Image caption UKIP's key negotiating objectives

It has warned the government against adopting any aspects of Common Fisheries Policy into UK law as part of its proposed Great Repeal Bill. This legislation will transfer existing EU laws applying to the UK onto the statute book before Parliament decides later which to keep and which to jettison.

Vessels from other EU nations, UKIP argues, should not have any form of "backdoor" access to UK territorial waters, with domestic fleets having sole entry to a 200 mile "exclusive economic zone".

EU officials have suggested the UK could have to pay up to £50bn to retain privileged access to the single market and to settle existing budget liabilities although a recent House of Lords committee report argued the UK would not be lawfully obliged to pay a penny.

UKIP will have little sway in Parliament when a vote is held on the final settlement as its only MP - Douglas Carswell - quit over the weekend and said he plans to serve as an independent. The party only has a handful of peers in the House of Lords.

However, UKIP has 20 MEPs in the European Parliament, which also has to give its consent to the terms of the UK's exit.

Labour set out its own six tests on Monday, including no dilution of the benefits the UK currently gets through the single market and customs union. It also warned against rushing the negotiations.