The UK’s flagship scheme aimed at improving private rented standards has come under fire for allegedly recruiting fewer than 1,000 landlords in its first year.

The London Rental Standard, a voluntary scheme launched by Boris Johnson for letting agents and landlords and which unites seven separate accreditation schemes, is seen as a template for other towns and cities throughout the UK.

According to City Hall, 14,350 private landlords – an estimated 12% of London landlords – have signed, together with 331 letting agents, managing an estimated 121,000 properties.

Labour said the scheme, launched a year ago, was failing, and that the Mayor would not achieve his pledge of signing up 100,000 landlords by this time next year.

However, the deputy mayor for housing in London, Richard Blakeway, said: “Most landlords own just one property, whereas signing up a single branch of a letting agency reaches an estimated 200 homes.

“This is a huge success in one year and we look forward to working with thousands more landlords and agents to help get a better deal for renters as this scheme grows.”

London Assembly’s Labour group said that of the landlords who counted as members, 13,512 were already members of the other accreditation schemes. It means there were fewer than 1,000 new joiners.

Member Tom Copley said: “We need real change in the private rented sector. Londoners need the peace of mind and security of longer tenancy agreements, caps on rent increases and an end to ‘no fault’ evictions.