THERESA May should take a “liberal” approach to post-Brexit migration, a former Conservative leader has said, as he compared leaving the European Union to taking control of a loaded gun.

Lord William Hague said it is possible to find a solution to exiting the EU without “shooting your foot off”. The senior Tory, who campaigned for a Remain vote in last year’s referendum, said he believes there is sufficient common ground among the different political parties to negotiate with the EU and secure a good deal for the UK after leaving the bloc.

But added he does not expect the negotiations to be easy, noting it is the “most complex task” any government has faced since the Second World War.

Speaking to BBC Radio 4’s Reflections with Peter Hennessy he said: “It has to be delivered now, Brexit.

“There is a way through actually because there is just sufficient space or common ground among the positions of the various political parties, the factions within parties, the business world and that can be negotiated with the EU and to me that means taking powers back, the sovereign powers back to the UK, leaving the EU, leaving the single market, but then using those in a very constructive way.

“Which means continuing to have quite a liberal approach on migration, which is essential to our economy in the short-term anyway, so we take back control but we use that to enter a strong free trade agreement, you know.

“And you can take back control of a gun but it doesn’t mean you use it to shoot your foot off.

“So let’s take back control but enter willingly as a sovereign nation into a very robust free trade agreement and with the right attitude on migration I think it’s possible to reach the right solution on trade.

“And I think that’s something that the Conservative Party could support across the board and that many business organisations and people in other parties could then support. So there is a way through, but I’m not pretending this is easy to arrive at, to negotiate exactly in that form.

“The Government faces the most complex task of any government since the Second World War. It is a very difficult one.”

Lord Hague also addressed other topics in his interview, including that he believed he could have done more to modernise the Conservative party and revealed his biggest regret was over the failure to resolve Syria’s civil war.

The former Foreign Secretary said: “I’m not sure there’s much more I could have done over that, but it is the great frustration.

“We came quite close in 2012 to agreeing with the Russians a settlement of the Syrian war and that’s, I think, the biggest scar.”

Earlier this month he gave his backing to Chancellor Philip Hammond’s proposals for a transitional Brexit deal, claiming it is the best way to stop Brexit becoming a “disaster” for the UK.

He warned a combination of sluggish economic performance, emboldened EU negotiators and a political stalemate in Westminster could lead to Brexit becoming “the greatest economic, diplomatic and constitutional muddle in the modern history of the UK”.

The UK Government has begun to publish position papers on Brexit, including one on plans for a temporary customs union with the EU.

Ministers say the new arrangement would allow the UK to strike new global trade agreements, while getting the benefit of tariff free trade with EU members.

Nicola Sturgeon dismissed the plan as a “daft ‘have cake and eat it’ approach, while it was rejected by the European Parliament’s Brexit coordinator Guy Verhofstadt as a “fantasy”.

May is seeking to move negotiations on to the issue of the UK’s future EU relationship, but the bloc has said it must first resolve divorce issues, including citizens rights, the exit bill and the Irish border.

“To be in and out of the Customs Union & “invisible borders” is a fantasy. First need to secure citizens rights & a financial settlement,” Verhofstadt said on Twitter.