Activists on both sides of the Scottish independence debate have hit the streets to convince voters to either stay or leave the UK at the start of the ­official referendum ­campaign period.

Glasgow-born actor David Hayman - known for his roles in The Boy In The Striped Pyjamas, Still Game and Rob Roy - joined Yes Scotland activists in the city's Hope Street to urge voters to seize "this wonderful chance to create a ­better and fairer Scotland".

Better Together campaign director Blair McDougall was also in Glasgow, joining unionist activists in Govanhill to tell undecided voters "why we are better and stronger together as part of the UK".

A cap on spending for groups on both sides of the debate came into force yesterday as the formal campaigning period begins.

It means Yes Scotland and Better Together cannot go ­beyond £1.5million each in the 16-week run up to polling day on September 18.

People and groups not registered as permitted participants are restricted to £10,000, but registered groups can spend up to £150,000.

Campaigners will also have to report any donations they receive over £7500.

Mr Hayman said: "This is the most exciting time in Scotland for more than 300 years. We have the opportunity, the wealth and the creativity to build a new nation built on pillars of fairness and social justice. We are rich in resources and rich in people. This is a once-in-a-lifetime opportunity to take responsibility for our own destiny and to make our own decisions.

"I cannot think of anything more exciting and inspiring and I would urge everybody, especially those who have yet to make up their minds, to have the confidence to say 'Yes'."

Yes Scotland chief executive Blair Jenkins said: "As we move into the formal phase of the campaign, more and more people are tuning into the debate. I'm delighted about that because this is a referendum with two very different narratives."

Mr McDougall said: "Today is another landmark in the ­referendum campaign as the financial rules come in to effect for all campaign groups. But today is also another day closer to the day when all of us in Scotland have to make the biggest political decision of our lives.

"The message from our campaign is clear, you don't have to make the black-and-white choice of separation; we can have the best of both worlds in Scotland. A vote to stay in the UK in September is a vote for more powers for our Scottish Parliament and a vote for the strength, security and stability that comes from being part of the bigger UK.

"We'll be campaigning everyday until September 18 to make sure all Scots have the facts about why we're better and stronger as part of the UK."

John McCormick, Electoral Commissioner for Scotland, said: "Campaigners have a vital role to play as they set out competing views for voters to choose between."