The commission said it would remove the posters

Large advertisements, on double-sided hoardings in east central Edinburgh, have been urging the electorate not to waste their vote at the 1 May poll.

But the posters do not refer to the Scottish Parliament election next Thursday.

They highlight the issue of education in Wales and show two children sitting in a classroom.

A spokeswoman for the independent organisation, which launched separate advertising campaigns in Wales and Scotland, said an investigation was now under way.

She added that the problem probably stemmed from an error at a distributor's depot. The commission said it would replace the posters as soon as possible.

The incorrect hoardings have been spotted on at least three different sites in Edinburgh.

'High impact'

One of the ads is outside the Meadowbank sports stadium which is on a main commuter route into Scotland's capital

The commission set out on its campaign by using TV, radio and billboard advertisements to persuade voters that they could "make a difference".

Its website's front page said: "As part of our role in raising awareness of the upcoming elections in May, we are undertaking a high impact advertising campaign.

"This year the campaign in Great Britain is focusing on the elections to the devolved institutions in Scotland and Wales."

The commission is an independent body which was set up by parliament in November 2000.