The company, the UK’s second largest postal operator, will handle over 3.75bn items of mail this year after winning business in a range of sectors including print, finance and retail.

One of the biggest contracts is Hotter Shoes, which typically mails 21m items a year, followed by outsourcing company Serco and Griffin Media.

Aside from Vistaprint, other notable new clients include Royal Liverpool NHS, direct marketing companies Meridian Delta and Kingsline, financial services company Admin RE and outsourcer Mittie.

Whistl would not disclose the value of the new contracts, which have all been secured in the past few months.

Chief executive Nick Wells said: “The new clients join over 6000 clients across the UK that trust Whistl to provide a quality and cost efficient service.

“I am delighted that we continue to grow and strengthen our leading position within the UK postal market.

“Our continued investment in core business divisions DSA and international, door drop media, packets and parcels and logistics are enabling us to broaden our client base and I look forward to announcing [further] new client wins in the coming months.”

Last month the business stopped its end-to-end (E2E) delivery service after private equity investor LDC, a division of Lloyds Banking Group, pulled out of a proposed investment to fund the further roll-out of the service. The move was understood to have put around 2,000 jobs at risk.

The company, which is a wholly owned subsidiary of Dutch delivery firm PostNL, was previously called TNT Post UK prior to a rebrand in September 2014. The business had been a subsidiary of TNT Group until 2011.

The company has UK depots in Leeds, Warrington, Bristol, Iver, Rugby, Coatbridge and Newtownabbey while its head office is in Marlow.