Theresa May's deputy says new Prime Minister must make 'positive case' for the UK

Speaking on the 20th anniversary of the Scottish Parliament, the Chancellor of the Duchy of Lancaster, said that strengthening devolution would require the UK Government to "listen and to act".

Boris Johnson and Jeremy Hunt are the two candidates remaining in the race to succeed Theresa May in Downing Street.

Mr Lidington said: "As we recognise this anniversary and celebrate the achievements of the devolved parliaments, we must also look to the future and how the governments of the United Kingdom can work together to deliver for citizens.

"Twenty years of devolution have strengthened the nations of the UK and improved accountability.

Tory candidates clash over Barnett formula and the Union

"Our vision for the nations of the United Kingdom is of strong devolved legislatures within a strong United Kingdom.

"Strengthening devolution also requires the UK Government to listen and to act. To support devolved governments to evolve and to champion them as the best model for the nations of the UK.

"It will be important for the new Prime Minister to make a passionate and positive case in every part of the UK for the benefits of being part of a strong United Kingdom."

On Saturday, the Queen attended the parliament with Prince Charles - known in Scotland as the Duke of Rothesay - to mark the 20th year celebrations.

Speaking in the chamber at Holyrood two decades after she officially opened the first elected assembly in Edinburgh, the Queen said that she had "watched Scotland grow and prosper" over the last two decades.

First Minister Nicola Sturgeon said: "This parliament is firmly established as the centre of this nation's public life. We have become the democratic institution which people look to, to reflect their priorities, values, hopes and dreams."

Presiding Officer Ken Macintosh said that over the last 20 years Holyrood had "grown into a self confident institution".