Waitrose managing director Mark Price has threatened to veto the potential tie-up between etailer Ocado and rival grocer Morrisons.

Price, who revealed he rejected an approach from former Morrisons boss Marc Bolland over a similar deal four years ago, said his lawyers will scrutinise any deal to ensure there are no breaches of contract.

He told The Telegraph: “I would never knowingly sign a contract with Ocado that agreed to them working with another retail competitor. We have moved to DEFCON 1 [on online expansion] because we don’t know where this is going to end up and we are now working on adding considerable extra capacity to Waitrose.com.”

It is understood that Waitrose is planning to open more “dark stores” across the UK to expand its own online deliveries. The retailer only has one at the moment, but it is thought this could rise to three, which will raise questions about the future of its partnership with Ocado.

The delivery agreement between Ocado and Waitrose is due to run until 2020, although it has a break clause in 2017.

Ocado, which confirmed last week that it is still in talks with Morrisons, said any agreement would be “complementary” to Ocado’s partnership with Waitrose, which would be “unaffected” by any potential agreement.

Waitrose owner John Lewis Partnership gave etailer Ocado seed capital when it was launched. The contract between the two grocers names the major UK retailers that Ocado cannot deliver for. Morrisons is one of the retailers named.

However, Ocado could do a less lucrative intellectual property deal with Morrisons, which would allow it to use the etailer’s delivery software under licence.