Nick Johnston, MSP for Mid Scotland and Fife from 1999-2001, said independence could help "kick-start" the country and achieve a better Scotland.
He said that Scotland needs the "grown-up powers" of an independent country to match its status as a "fully developed grown-up country".
He said: "Having followed the arguments of the Yes and No campaigns, my conclusion is that while a devolved parliament can do good things - and it has - it lacks the core economic and welfare powers to tackle the fundamental issues.
"Put simply, while problems and opportunities with particular resonance in Scotland can go by the board at Westminster, it's just not possible for that to happen in a Scottish Parliament."
He added: "A new Scotland vested with full powers and full of ambition will be the kick-start I believe we need as a country."
Mr Johnston also called for the voice of Scotland's centre-right to be heard, and welcomed the launch of the Wealthy Nation initiative last week by voices from the centre-right who back a Yes vote.
The independence referendum will take place on September 18 next year.
The Scottish Government last month published its White Paper on independence, outlining how it believes a Yes vote in next year's referendum could pave the way for a new era for the nation.
The 670-page paper sets out how independence could have an impact on all areas of life, including currency, taxation, childcare and education, pensions, welfare, defence and broadcasting.
Blair Jenkins, Yes Scotland chief executive, said: "Nick Johnston's backing for a Yes vote highlights the fact that a fully empowered, independent Scotland has increasing appeal across a broad political spectrum.
"He hits the nail on the head when he says that only a Yes vote will give Scotland the opportunity to fully realise our great potential and ambition.
"We know that the more people learn about the benefits of independence the more likely they are to vote Yes and Mr Johnston's support underlines that."