The last of Whitehall's "manifesto for the union" reports may be released just weeks before Scots vote on independence, it has emerged.

Despite the heavy criticism a trail of one of the papers attracted earlier this year, Coalition sources insist they are pleased with the impact they have had and are not rushing future publications.

The UK Government had initially been due to release all 13 policy documents by the end of this year.

But to date they have published just four - on the legal basis and history of the UK, microeconomics, the financial services industry and the currency options for an independent Scotland.

A number of other reports in the series are due to be published shortly.

A Coalition source said there was no rush to release all the papers. "This could last well into next year," he said.

It is thought that the UK Government could be forced to release the last of the papers at least 16 weeks before polling day, almost six months later than originally planned.

The UK Government reports have been attacked by the Scottish Government as scaremongering.

There was staunch criticism this year when a preview of one of the papers warned of the possibility of mobile phone roaming charges between an independent Scotland and England, an issue already being tackled by the EU.

SNP MP Pete Wishart said: "Previous stories from UK Government sources made a virtue of publishing all the reports this year, and it's pretty obvious what has happened. Scotland is always an afterthought in Whitehall, and these reports have slipped because of the effort being put into the referendum to exit the UK from Europe."