Pinsent Masons will double its fee income target from its freelance lawyer service Vario after client demand vastly outstripped original expectations in the first 18 months of the scheme.

Launched in February 2013, the initative took two and a half times its target revenue in its first year, and now has more than 100 lawyers on its books.

"We had a strong sense that this was something that the market wanted," says Pinsent's partner Alison Bond, who leads the initiative with support from Katherine Thomas, Vario's director of members and operations.

"Since our launch day the phones haven't stopped ringing and the emails keep coming in….It's across our client base. There isn't a sector or practice area that hasn't been penetrated by this scheme."

Vario is designed as a flexible service for in-house teams to cover fixed-term projects, maternity leave or peak periods of demand with Pinsent's legal staff.

These can range from newly qualified lawyers up to those with experience at partner or general counsel level. Unless the client asks for additional support, the scheme normally provides one lawyer per project.

The firm would not be drawn on what its fee income from the scheme was, but said that doubling the target would set a challenging goal for the next 12 months.

Pinsents operates a "rigorous" selection process, involving application forms and interviews to find out why the lawyer wants to work in the freelance scheme, as well as technical expertise, which helps place them with an appropriate client.

"A good freelancer is someone who doesn't ruffle feathers and can fit right in." says Thomas. "We thought hard about how we could get this quality in our Varios, so we look at their degree of flexibility and how much they would enjoy working in that way."

The use of on-demand legal services has become increasingly popular in recent years. Eversheds has nearly doubled the number of lawyers in its own freelance pool over the last two years. The temporary lawyer headcount in the firm's Agile scheme has gone from 80 in March 2012, when the service was made a permanent fixture at the firm, to its current 150, according to Graham Richardson, the partner responsible for the scheme.

Eversheds also did not provide overall revenue figures for the initiative, but said that 50% growth has been archived every year it has been in operation, with this year's income also increasing by 50%.