Labour today refused to be drawn on claims the daughter of retiring Glasgow East MP David Marshall operated two private firms from the Marshall family home which also houses Mr Marshall's publicly-funded office.

Labour today refused to be drawn on claims the daughter of retiring Glasgow East MP David Marshall operated two private firms from the Marshall family home which also houses Mr Marshall's publicly-funded office.

Reports claimed Christina Marshall registered the property companies based at her father's home in March. The story comes just two days before the crucial Glasgow East by-election.

Scotland Office Minister David Cairns, who is managing Labour candidate Margaret Curran's campaign, said: "As far as we are concerned, David Marshall stood down as an MP on doctor's orders.

"Two doctors' letters said he wasn't fit to carry on, and we have accepted that."

Meanwhile the SNP today claimed to be making up ground today as the by-election reached its closing stages.

Party deputy leader Nicola Sturgeon said voters were switching from Labour to her party and the SNP was feeling "extremely optimistic".

"Our support is strong and motivated and it's growing by the day," she told BBC Radio Scotland's Good Morning Scotland programme.

"We detect in Glasgow East a very strong mood to send a message to Labour - a message that says people are very unhappy with a London Labour Government that is deeply out of touch and is doing absolutely nothing to help individuals with the rising cost of living."

And she claimed: "This is a very close-run election and all of the movement is towards the SNP."

Asked if her party would win, she said: "We are very optimistic and we certainly intend to win."

Ms Sturgeon also defended her party's plans for a local income tax to replace the council tax.

A joint report by the Chartered Institute of Public Finance and Accountancy will today reportedly warn that the SNP's plans for a 3p rate of local income tax to replace the council tax will create a £742 million deficit.

Ms Sturgeon said the report assumed that Scotland would no longer receive the council tax benefit, which would be an "outrageous and unwarranted" state of affairs, and it also ignored extra central government investment.

SNP candidate John Mason will be joined by celebrity supporters and First Minister Alex Salmond.

Braveheart actor James Cosmo and comedienne Elaine C Smith will boost the party's profile with a shopping centre visit.

Labour's campaign today included a visit to a hi-tech employer in Glasgow East with the aim of promoting a positive vision of the area.

Candidate Margaret Curran said: "I will never, ever talk the east end down.

"The people in this community are sick and tired of being talked down - from the Nationalists comparing the area to the Gaza Strip to sneering Tory commentators deliberately ignoring the improvements of recent years.

"Nowhere is this more true than in the case of employment in the area, where local employers are bringing high-skilled jobs to the east end.

"What we need to do is get more people off benefits and into work at places like the one I am visiting today."

Tory activists will canvass voters on the cost of living and crime, while reinforcing their message to reject separatism.

Scottish Tory leader Annabel Goldie said her party was making sure voters realised they did not have to settle for "the failure of Labour or the risk of the SNP".

She also argued that the SNP was soft on law and order.

"The Scottish Government under the SNP does not want to grip the thistle and commit to the new prisons we need," she told Good Morning Scotland.

Liberal Democrat candidate Ian Robertson has cancelled all campaigning activity this morning due to a family emergency.

He had planned to join activists going door-to-door in the constituency.

His spokesman would not comment on the nature of the family emergency.

Voters will go to the polls on Thursday in a constituency made vacant by the resignation of Mr Marshall.

Labour is defending a majority of 13,507 over the SNP.

SNP claims of a movement of voters towards it was rejected by Labour, which said the reverse was happening.

Ms Curran's campaign took her to Walker Precision Engineering, which employs 126 people developing and producing machines to meet rising world demand for biometric passports.

The visit was intended to counter the impression of the east end as a depressing and run-down area.

Ms Curran said: "I think there has been a bit of a shift towards Labour.

"I think the decisive change in the last week has been the need for someone to articulate the strengths of the east end of Glasgow and stand up for it when it is required."

Labour has also distributed thousands of personalised messages to voters who have promised the party their support.

Each message, resembling a page from a ring binder notebook, carries the name and address of the intended recipient and a localised message.

Scotland Office Minister David Cairns, managing Labour's campaign, said the image of Glasgow's east end had become a huge issue in the campaign.

"People are sick of how it is being presented on the TV news, and on the media," he said.

He went on: "They are also sick of the collusion between the SNP and the Tories to pretend that nothing has happened in this area and that nothing is getting better when there are nine new primaries, three more on the way, and two new secondary schools covering the constituency."

And he said: "The way the area has been presented as the Gaza Strip all the way through has really got people's backs up."