Holyrood bosses decided they were not happy with the giant "Public Entrance" sign outside the front of the building. The final "E" was four millimetres too high, they said.

So contractors (pictured above) were summoned back yesterday to put matters right.

A spokeswoman said: "It involves a bit of stonework and a bit of paint. We will have a look at it when it is finished today and check we are happy."

The giant granite sign was criticised as unnecessary and extravagant when it was first proposed. But parliament officials insisted research showed signage needed to be improved and materials had to be of appropriate quality for a World Heritage Site.

The £414 million parliament building was opened in October 2004, but visitor numbers have not matched experts' forecasts.

The irregular-shaped sign, which measures 5.9 metres by 1.1 metres, was due to go up towards the end of April, but finally made its appearance three weeks later.

Then, yesterday, the area immediately in front of the sign was taped off again.

A workman with a spirit level told a passer-by the sign was "squint".

But parliament officials said the contractors had been asked to come back to "sharpen up" the lettering.

And one workman was later seen using a chisel on the sign, which reads "Scottish Parliament Public Entrance" in English and Gaelic.

Edinburgh Pentlands Conservative MSP David McLetchie said: "It's probably just another example of how ill-fated most aspects of the construction of this building have been and it continues true to form."

Last week the Evening News revealed the parliament had spent over £250,000 on a traffic light system and new barriers to control the entrance and exit to the MSPs' underground car park.

Mr McLetchie said he had not noticed any problems with the sign. "I have not studied it that closely, but in so far as it told us where the public entrance was it seemed to do that effectively.

"But if the design is not right, we shouldn't pay for what we didn't order."

Lothians Labour MSP George Foulkes said most people would not have noticed any problem with the sign.

"It would have been better just to leave it," he said. "If one of the letters is not quite right it could have become a curiosity like a stamp with a misprint."

The parliament spokeswoman said: "It's a minor correction. The last E of entrance was four millimetres too high. We felt it was not what we had asked for."

But she stressed the work was being carried out at no extra expense to the parliament.