Theresa May is to announce £2bn in extra money for housing associations over a decade, arguing that secure long-term funding for new schemes is one of the key ways to ease the housebuilding crisis.

Speaking at the National Housing Federation (NHF) summit in London on Wednesday, the prime minister will promise longer-term cash for housing associations, asking in return that they take more of a lead in building their own large-scale developments.

In a sign of the gradually-shifting tone of government rhetoric on housing, May will also specifically praise social housing, saying too many politicians still “continue to look down” on it.

The main announcement of the speech is £2bn in what is described as new funding for social and affordable housing. This can be applied for over a period stretching to 2028/29, intended to help long-term construction decisions.

Downing Street said May would be the first prime minister to address the summit of the NHF, which represents housing associations. In extracts of the speech released in advance, May will say she had been told the sector needed “the stability provided by long-term funding deals.

“Doing so will give you the stability you need to get tens of thousands of affordable and social homes built where they are needed most, and make it easier for you to leverage the private finance you need to build many more.”

In return, May will say, housing associations should use their expertise, local connections and long-term planning “to achieve things neither private developers nor local authorities are capable of doing.

“Rather than simply acquiring a proportion of the properties commercial developers build, I want to see housing associations taking on and leading major developments themselves.”

Last year the government announced a total of £9.1bn in public funding for council and housing association homes.

Housing associations have been told the £2bn is entirely new money, and are understood to be pleased at the longer-term allocation of the money, saying it will make construction planning more feasible.

May has repeatedly tried to address the affordability and supply crisis in housing, which has seen home ownership become an increasingly unrealistic prospect for many younger people.

May’s speech acknowledges the new reality by praising social housing, not something done often by Conservative leaders of the recent past.

“For many people, a certain stigma still clings to social housing. Some residents feel marginalised and overlooked, and are ashamed to share the fact that their home belongs to a housing association or local authority,” she was to say.

“And on the outside, many people in society – including too many politicians – continue to look down on social housing and, by extension, the people who call it their home.”

She is also expected to add: “We should never see social housing as something that need simply be ‘good enough’, nor think that the people who live in it should be grateful for their safety net and expect no better.”

May said she wanted to see “social housing that is so good people are proud to call it their home,” adding: “Our friends and neighbours who live in social housing are not second-rate citizens.”