Media playback is unsupported on your device Media caption Mark Williams calls for a "healthy bit of caution" on Brexit

A second referendum is needed before Britain leaves the EU in case the exit deal "wrecks the future for our children", Welsh Liberal Democrat leader Mark Williams has said.

The party launched its Welsh manifesto on Friday and said the referendum was "at the heart" of its proposals.

Mr Williams said voters should have the option to reject the deal and remain in the EU if they do not like the offer.

He was joined in Hay-on-Wye, Powys, by ex-deputy prime minister Nick Clegg.

The Lib Dems said the manifesto, published online in advance of the official launch, plans for a stronger Wales in a fairer UK.

The document says "when the terms of our future relationship with the EU have been negotiated (over the next two years on the Government's timetable), we will put that deal to a vote of the British people in a referendum, with staying in the EU as the alternative option on the ballot paper".

Image caption Nick Clegg (right) and senior Welsh Lib Dems visited a pharmaceutical firm near Hay-on-Wye

Mr Williams said: "A bad Brexit deal, with Britain outside the single market, will wreck the future for our children, our economy and our schools and hospitals."

He added: "Our plan comes from a strong, open and tolerant Wales, where our children have the best start in life, where people are decent to each other and where our economy works for everyone."

Mr Clegg said there was a lot of evidence that people were concerned about Brexit.

"If we get it wrong... this will really hit people where it hurts, in their pockets, in terms of prices in shops," he said.

"People want a sensible approach, including having a say at the end of it all."

The manifesto also promises Liberal Democrat MPs would "resist a power grab" of Welsh Assembly powers during the Brexit process and would "drastically reduce the number of powers reserved to Westminster and prevent Westminster from being able to override Wales on devolved matters".

Other pledges include:

Giving more financial powers to Welsh ministers

Seeking to increase the Welsh Government's funding from the UK Treasury

Transferring powers over transport, all Welsh ports, energy, broadcasting, air passenger duty, youth justice, policing and other justice powers from Westminster to Cardiff Bay

An additional £7.5m for community policing across Wales

Electrifying the north Wales main rail line and funding for a feasibility study into re-opening rail links between Aberystwyth and Carmarthen

Investing in the South Wales Metro

Giving the immediate go-ahead to the Swansea Bay tidal lagoon

Putting a penny in the pound on income tax, enabling Wales to spend an extra £300m on the NHS and social services

Ending the public sector pay freeze for NHS workers

The Liberal Democrats are also committed to scrapping police and crime commissioners, introduced under the previous UK coalition government they formed with the Conservatives.

They would also seek to give the Welsh Government the power to set its own bank holidays, allowing it to make St David's Day a national holiday in Wales if it wished.

At the 2015 general election, the Liberal Democrats won one seat in Wales.