Patrick Deuchar accused the heritage department of "point-scoring" and leaving him with egg on his face.
"For whatever reasons the department apparently decided there were points to be scored by leaking this story early," Mr Deuchar told the official announcement of the grant and improvement plans.
"I think that is a disgraceful situation and one not to be condoned. We have been working for six-and-a-half years on this project and instead of being excited by today we are very disheartened.
"Having said that, it is still a very exciting moment for us."
New features planned for the 125-year-old Royal Albert Hall, in Kensington, west London, include bars, restaurants, terraces and piazzas.Reuse content