Sigh, it's very old news.
Is the government entitled to have a say on the matter? Yes. As was done before, and not just in EU-related matters; from wars to public sector bruhaha -- the government always has a formally agreed position communicated to the public.
Is their stance to leave the EU? No.
They should be neutral! No. They are not the Queen, the Royal Family, the Beeb or the Civil Service.
But should they use the Civil Services' research? It's available to both sides of the argument and the public. Want to use the Civil Service yourself? Get elected!
Should they be allowed to spend the money? Do not confuse the government and the yet-to-be-officially-designated In campaign.
The PM is a scoundrel! He's going, just like Merkel and other caricature pantomime villains of the Brexit myth. His picture isn't on the materials. Chill.
Here's the document:
https://www.eureferendum.gov.uk/why-the-government-believes-we-should-remain/eu-referendum-leaflet/.
Pretty mild stuff.
The Wilson version was far more ideologically charged. But then again, even if it said: 'After much deliberation, we recommend to leave the EU.' The Leave camp would still cry 'unfair representation'.

Only if they could agree on their platform, it might make some semblance of sense; but alas, tis too much work, too much detail!
Lastly, the ministers in the Leave group knew Cameron's stance, campaigning tactics and attitude towards winning, indeed they benefited form it, and now cue surprised indignation -- weak. The quitters knew whom they picked a fight with, they are now getting it.