He claims that more than 15,000 people aged 65 to 74 in the Borders will not get a new, improved flu jab because Holyrood ministers ordered it too late.
Health experts recommended last October that over-65s should be given a new, dearer multi-purpose flu jab called Fluad as it boosts the immune system as well as protecting against the virus.
The UK Government’s joint committee on vaccination and immunisation believes the vaccine will help cut hospital admissions for the elderly.
In England, all over-65s will be eligible for the vaccine after it was ordered in time for this winter.
However, health bosses north of the border did not order Fluad until March this year, meaning there is only enough of the drug to offer it to over-75s.
An estimated 15,714 Borderers aged 65 to 74 will not be offered the latest vaccine.
Berwickshire, Roxburgh and Selkirk MP Mr Lamont said: “The Scottish Government has repeatedly mismanaged winter pressures on our hospitals, and this mistake, before the season has even started, does not bode well.
“A cut-price and less effective flu jab is the last thing our tireless doctors and nurses at NHS Borders need in the run-up to the winter months.
“By failing to place an order in time, more than 15,000 pensioners in the Borders will not be as well protected against flu as they could have been.”
NHS Borders says Fluad will be available to all those over 65 from next winter.
A spokesperson for the health board said: “A new adjuvanted trivalent influenza vaccine (aTIV) has recently been recommended for use to compensate for the weaker immune systems of older people.
“Over the next couple of years, we are phasing in aTIV, starting with those aged 75 and over this winter, followed by those aged 65 and over next winter.”
A Scottish Government spokeswoman added: “This vaccine is currently produced by only one company, who were unable to give a guarantee on supplying the new vaccine for all over-65s in time for this year.”