Senior figures from the charity sector have clashed about the impact of a Yes vote in September's independence referendum.

Gavin McLellan, an executive member of the Institute of Fundraising Scotland, said he was "'very optimistic'' for the sector if the vote is to leave the UK.

But Duncan Tannahill, a trustee of deaf-blind charities Sense UK and Sense Scotland, likened voting for independence to buying a housing and getting a mortgage for it without knowing the full costs involved.

Speaking in a personal capacity, Mr Tannahill, a former chief executive of Glasgow Chamber of Commerce, said: "The nationalists have failed to answer the key questions in this debate: what currency we would use, the terms and timeframe of our membership of the EU, the costs of setting up the new Scottish public agencies that would be required, our credit rating and its impact on borrowing costs and more.

"No-one would buy a house and get a mortgage without knowing the costs involved, from the price of the house to the interest rates, and yet that is exactly what the nationalists are expecting the people of Scotland to do."

He added: "Scotland has enjoyed the powers of devolution for more than a decade.

"More devolved powers are already established and will become effective in 2015. The major UK parties have promised more changes in the future to a Scotland which is part of the UK.

"Simply put, I can clearly see that we have the best of both worlds already and I will vote No to protect that fact for my family and indeed all Scots."

But Mr McLellan told the Daily Record that "following a Yes vote, major trusts and foundations will have the opportunity to continue to support some of the very best work in the third sector across the British Isles".

He argued: "'Current UK-wide trusts and foundations will not want to miss these opportunities in an independent Scotland.''

His comments were welcomed by SNP MSP Annabelle Ewing, who said: ''People in the third sector understand that independence is not an end in itself but a starting point to build a fairer and more compassionate Scotland.''

She added: ''The SNP Scottish Government is committed to building a more equal Scotland. Scotland's vibrant third-sector organisations will play a key role in helping deliver that.

''But we can't allow Westminster to keep holding back progress on tackling poverty and inequality.

''Only a Yes vote will enable us to tackling these social ills and take a huge step towards delivering a fairer Scotland.''

Shadow Scottish secretary Margaret Curran said Mr Tannahill's comments were a "significant intervention from a man who knows Glasgow well and has a strong track record of delivering for the city".

She added: "The closer we get to the referendum the more people are thinking seriously about the impact leaving the UK would have.

"As part of the UK we can have the best of both worlds for Scotland.

"We can have our strong Scottish Parliament, with the guarantee of more powers for Scotland, backed up by the strength, security and stability of being part of the larger UK. Only separation puts that at risk."