Britain risks being "pushed over a cliff edge" with a bad Brexit deal, prominent Leave campaigner Lord Owen will warn.

The former SDP leader will call on the UK Government to starting striking independent trade agreements with other countries now, before Brexit negotiations begin next year.

The peer will also use a speech in Switzerland on Thursday to say the government should carry over all EU laws into UK domestic law.

He will say: "The UK has to be able to start negotiating international trade agreements before exit. This is a non-negotiable issue. So is the UK having full World Trade Organisation membership in our own right.

"To fail to have these two issues put into operation and sanctioned under UK law in the European Communities Act legislation would be gross negligence.

"Under any of the options for negotiating we must have these safeguards or we otherwise face being pushed over a cliff edge after waiting for an EU decision in 2018-9 which might prove to be unacceptable."

Lord Owen insists that if the EU blocks British trade negotiations with non-EU members, the government should refuse to exit under Article 50 of the Lisbon Treaty but instead use the Vienna Convention on the Law of Treaties to withdraw.

He will also claim the adoption of all EU laws into UK domestic law will simplify the process of Brexit negotiations.

Lord Owen will say: "The government will introduce UK legislation on the European Communities Act 1972. If they are wise, through one clause they will carry over all EU law into UK domestic law.

"That means at the outset of the negotiating process nothing will change.

"There will be a political commitment to not make any changes in the European Economic Area Treaty on trading and Customs Union issues without the agreement of the EU Council of Heads of Government prior to the exit procedure being put in place."