Image copyright PA Image caption Lottery winners Colin and Chris Weir have given £5.5m to the SNP and the Yes Scotland campaign

Lottery winners Colin and Chris Weir have given a further £1m in donations to the SNP, according to the Electoral Commission.

The register of donations for the first three months of 2014 shows Mr and Mrs Weir each gave £500,000 to the party on 10 February.

This brings their total contribution to the SNP and the pro-independence Yes Scotland campaign to £5.5m.

The couple, from Largs, Ayrshire, won £161m on EuroMillions in 2011.

Earlier this month, the couple wrote a letter to newspapers calling for an end to the "smears" that they said accompanied their donations.

The couple said the donations had led to them being subjected to "downright nasty" personal attacks.

The Weirs' latest contribution comes on top of the £1m they donated to the SNP in September 2011, and the £3.5m they have donated to the Yes Scotland campaign in the last two years.

They have used their fortune to fund a number of good causes, including buying a 13-year-old boy a prosthetic leg, and have established a charitable trust to help fund health, sport, cultural, recreational and animal welfare projects.

An SNP spokeswoman said: "We thank all of our donors - big and small - for contributing to the success of the party, including consistently being ahead in the polls after eight years in government, which is a remarkable achievement.

"The SNP has never been in better shape - with a record membership of over 25,000 - and we are fighting fit to help achieve the Yes vote in September."

However, Scottish Labour's constitutional spokesman Drew Smith said: "The Weirs are entirely entitled to spend their lottery winnings as they wish but the revelation that the SNP and the "Yes" campaign are relying on just one family for their funding does rather undermine the nationalists' claims of a broad based grass roots campaign."

Elsewhere, the Electoral Commission register of donations also showed that the UK Conservative Party had received £6,662,232, with more than a fifth coming from a single donor - British-Australian hedge fund boss Sir Michael Hintze, who donated £1,506,500.

Labour received £4,409,167 with two-thirds of it coming from the unions Unite, Usdaw and Unison.

The Liberal Democrats received £1,074,482 in donations.