"An advert says the role has an annual salary of £50,000 pro rata and is "rooted in Walthamstow not Westminster".
The "locum MP" will cover constituency work over seven months and will not sit in the Commons or vote.
Ipsa - the body which regulates MPs' pay - says it provides extra funding for all MPs' offices to cover absences.
MPs themselves are paid in full for the whole period of leave.
The locum MP will represent Labour MP Ms Creasy - who has previously spoken out about the maternity rights of MPs - in constituency surgeries, at events and visits and will answer queries from constituents.
Locum is a word most often used in the medical profession to describe a doctor who is covering the duties of another physician while they are ill or absent from work for some other reason.
The "locum MP" advert says in "the last few years alone" Ms Creasy, who represents Walthamstow, in North London, has answered more than 133,000 queries, in addition to her staff.
It adds that the role will begin in November and will "play a key role" in ensuring Ms Creasy's campaigns progress until May 2020.
She will be represented in Parliamentary votes via a proxy - an MP who is allowed to vote on a colleagues' behalf.
MPs have previously arranged unofficial cover for their constituency work through their staff or colleagues.
Ms Creasy said: "If the place that makes the law doesn't recognise the value of ensuring cover for the duties of MPs, then how can it advocate for the millions of parents across the country worried that if they take time out to care for newborn children they will suffer?
"As yet Parliament has still to get its act together to come up with a policy on this area and has not yet even begun to consult on the issue as promised, but this post means residents in Walthamstow can be confident that when my child is born they will still have someone to take up their cases with ministers, local public services and an advocate for the causes they care about."
In June, Ms Creasy wrote in the Guardian that she was being "forced to choose between being an MP and a mum" because Ipsa does not automatically provide paid cover for MPs on parental leave.
Responding to the general issue rather than Ms Creasy's specific case, Ipsa's chairwoman Ruth Evans said: "To provide MPs with extra money, Ipsa asks for an explanation to be provided of how the additional money would be spent.
"We support proposals to allow maternity cover for MPs, and this would be for the House of Commons to take forward.
"In the last few years, we have more than doubled the funding available for MPs' dependants to support family life and will continue to strive to modernise our rules."
In January, MPs backed a year-long trial to allow MPs who were about to give birth or had recently become a parent to nominate another MP to vote on their behalf in the Commons.
Ipsa said that during the pilot it will pre-approve any applications for staff cover for MPs' parliamentary functions during their period of parental leave - and then consider creating a new budget to put the scheme on a permanent footing.
The debate over Parliament's rules was reignited earlier this year when Labour MP Tulip Siddiq delayed a Caesarean section to attend a vote on Theresa May's Brexit deal.
Later that month, the Hampstead and Kilburn MP became the first to vote in the Commons by proxy".
In nearly all sectors of work it is common for temporary cover to be taken on to cover those on Maternity Leave and Walthamstow a major district in North East London and is part of the London Borough of Waltham Forest. It is located 7.5 miles (12.1 km) North East from Charing Cross. is close to Westminster but difference if it was Orkney & Shetland and this should become common place practise.
We often fail to recognise the amount of consituency work outside parliament and Y Senedd and the people need to see that they can have access it.
The sight of serious ill MPs being delivered by ambulance to take part in a crucial vote is an appalling indication of our democratic system.
Incidentally I believe that that If an MP was to die in the Houses Parliaments it would not be registered as such due to our arcane laws.