The phrase 'which was promised' is correct and usable in written English.
You can use it when referring to something that was promised in the past and either kept or not. For example: "The government has failed to deliver on the improvements which was promised."
The assistance which was promised from Kabul has not been provided.
MPs will get only 90 minutes to debate the ban on fox hunting before the vote, which was promised in the Conservative manifesto.
The vote, which was promised in the Conservative manifesto, is now almost certain not to pass, as Labour will also vote against it.
How I would like to see real diplomacy, which was promised to us this last election, and not the hypocritical words (and actions) of the past years.
The vote, which was promised in the Conservative manifesto, is now almost certain not to pass, as Labour will be whipped to vote against it as well.
And the event was boycotted by the Iraqi journalists' union, which was promised plots of land for its members earlier this year by Mr. Maliki.
Big developments in long-distance transmission lines, which are promised, could be most valuable of all.
What the typical American probably cares about more is raises, which were promised in spades.
People must be warned of the future which is promised to them by their enemies.
Twelve Chinook helicopters which were promised by the government in the autumn's defence review may also become casualties of the cuts.
At some point, perhaps, the series of appeals which are promised by Mr Calley's defence lawyer will escape from the reticence of the military process into the relative light of the civilian courts.
