Almost three-quarters of GP practices will reportedly open as normal on Thursday when doctors take industrial action for the first time in almost 40 years.
A poll by Pulse magazine said only a quarter of practices across the UK have notified their primary care organisation that they will be taking part in the strike.
Across 20 primary care organisations, 281 out of 1,265 practices have so far notified NHS managers they are taking action.
Up to 100,000 doctors who are members of the British Medical Association (BMA) could be on strike in protest at the Government's pension reforms.
Last week Pulse reported that hundreds of GP practices were notified that they could be hit with compensation claims from NHS managers if they are found to be in breach of contract.
It said that PCT clusters in London wrote to all 1,331 practices in the capital, saying: "The local NHS may decide to withhold certain payments due to a contract holder by way of compensation for any breach, should it occur. In addition, formal contract breach notices would be issued."
The Royal College of Midwives has advised its members not to do anything to "undermine" the industrial action. It urged members to "work as normal" on Thursday.
According to Health Secretary Andrew Lansley, the planned strike could see up to 30,000 operations cancelled, 58,000 diagnostic tests postponed and 200,000 outpatient appointments rescheduled.
Mr Lansley also said up to 1.25 million GP appointments would be pushed into the days and weeks following the action.
The BMA announced the strike last month after it accused ministers of pressing ahead with "totally unjustified" increases to pension contributions and a later retirement age for doctors even though a deal on pensions was agreed four years ago.
All non-urgent work will be postponed, the BMA said, adding that although the action will be disruptive, doctors will ensure patient safety is protected.
Doctors will see anyone who is ill, or who believes they are ill, on the day of action but will not do paperwork.
Local NHS managers have urged patients to only use services if there is an urgent need.
Most doctors will be taking industrial action for the first time, with the last dispute almost 40 years ago.
Mr Lansley has once again written to the BMA reminding them the final offer of a pension of £68,000-a-year was non negotiable.
He urged the union to think again about the action.
"The BMA say doctors feel that changes to their pension scheme are unfair and unnecessary," he said.
"This suggests that they do not feel any change to their pensions arrangements are justified - but change is necessary and our proposals are fair."
Doctor Sarah Wollaston, Tory MP for Totnes and former GP, said that many doctors had contacted her telling her they were unhappy with the action.
She said: "Any group of people faced with the prospect of paying more towards their pensions and working longer would be upset about that but as time has gone by, doctors have found that the public are not sympathetic to this because doctors' pensions are far better than most of their patients.
"It is very clear that there is no room for negation on this. The idea that this is a victimless strike is incorrect.
"Most doctors, when it comes down to the day, will be putting their patients first. Just talking to GPs I know, many of them are telling me that they are planning to work but might put a notice of support or something in the window."