The creditor said Greece's public debt had become "highly unsustainable" and it needed relief from its debts.
The BBC's economics editor Robert Peston said the criticism was savage. The IMF suggested options including writing down the debt - a move most fiercely resisted by creditors.
The Greek parliament must pass four pieces of legislation on Wednesday.
It is the first requirement of the deal offered after hours of negotiation in Brussels on Monday.
Why on earth should Greek MPs vote for a painful economic reform package which the IMF - the supposed global arbiter of these things - does not believe will put the country back on the path to prosperity?
The eurozone creditors, and Germany in particular, forced Alexis Tsipras - against his strong preference - to accept IMF participation in the next formal bailout package to be negotiated if Greek MPs pass the initial reform measures tonight.
They told him, in effect, he would be turfed out of the eurozone and into national ruin unless he took more of the IMF's money and fiscal bossiness.
Which also look tragically comic tonight - with the IMF saying that if it's all the same to Mrs Merkel, it would rather not touch Greece with a barge pole.
Or to be tediously literal, the IMF has made it clear that it does not wish to participate in any further Greek bailout, unless Germany and the rest drop their vehement opposition to big write-offs of Greek debt.
Which should be music to the ears of Mr Tsipras, except that presumably he would quite like his creditors to agree among themselves, before presuming to tell him how to run his own shop.
