Investment platform Interactive Investor (ii) has agreed to acquire smaller rival Alliance Trust Savings (ATS) from parent Alliance Trust in a deal worth £40m.

The deal also includes Alliance Trust’s Dundee office building, where ATS is based.

ii currently has assets under administration (AUA) of £20bn and over 300,000 customers. The deal, which is subject to regulatory approval, will boost ii’s AUA to £35bn and client base to 400,000.

ii CEO Richard Wilson said: “The acquisition brings together the country’s two largest fixed price providers, adding significant scale to ii, and reinforcing our ability to deliver excellent choice, value and service to all our customers.”

The deal is the latest move by Alliance Trust to focus on its global equity portfolio. The sale proceeds will be invested in this portfolio.

As part of this strategy, Alliance Trust has previously sold its investment management arm Alliance Trust Investments to Liontrust. The trust recently also announced the sale of certain non-core holdings in private equity assets to PineBridge Investments.

Alliance Trust chairman Lord Smith of Kelvin said: “The two businesses are highly complementary and ATS customers, many of whom are Alliance Trust shareholders, will benefit from Interactive Investor’s similar low flat-fee structure, as well as its increased scale and focus.

“A key consideration for the Board was a commitment to maintaining ATS’ presence in Scotland. We are therefore very pleased that ii plans to invest in ATS’ Dundee operating centre.”