Britain's biggest digital bank will offer its legion of loyal customers mobile phone contracts starting from this summer. 

Monzo banking customers will be able to sign up to one of Monzo Mobile's new Sim-only phone plans for as little as £8 per month.

Monzo also plans to reward loyalty by giving users 5 per cent off their monthly bill each year, rising to a maximum of 30 per cent over time. 

This is in contrast to many other Sim-only contracts, where the price can be hiked after an initial contract period ends.

It has not ruled out the annual inflation-linked price rises common to many phone contracts, though. When asked by This is Money it said there wasn't a 'commitment' to making them 'at this stage'. 

Monzo Mobile will use the infrastructure of the Virgin Media O2 network, which is already used by Sky Mobile, Tesco and Giffgaff. 

Customers will be able to use the existing Monzo app to keep track of their phone payments alongside their banking. 

Monzo Mobile will only offer eSims, which must be switched digitally on in your phone's settings. Customers won't be able to have a physical Sim card. 

A waiting list has opened today, where customers can register their interest ahead of the full launch later this summer.

Monzo said Monzo Mobile will be free from hidden fees or surprise charges, with customers able to switch or cancel at any time with no exit fee.

The plans will be monthly rolling contracts, so can be cancelled at any time. Data is also capped and not charged per use. 

The prices charged for each of the plans will be the same for both new and existing customers. 

For £8 a month, Monzo Mobile customers will get 10GB of UK data. 

This isn't the cheapest on the market, but the price is competitive. 

A check on comparison site Uswitch reveals the cheapest 10GB Sim-only deal is with Spusu mobile and costs £5.90 per month, for a one-month rolling contract. It also includes EU roaming, which Monzo's plan does not.  

With Monzo, a 30GB plan will also be available for £12 a month. This will offer 10GB of Europe roaming data as well. 

For those looking for a similar plan, there are cheaper options with more data. For example, Talkmobile offers 50GB of data for £6.95 a month, including roaming in 46 countries. 

Monzo Mobile's Unlimited plan will cost £20 a month. This will give customers unlimited UK data and 26GB of global roaming data. 

This price is comparable to others on the market, though some are slightly cheaper. On Uswitch, there is an ID mobile contract offering unlimited data for £15 per month with roaming up to 30GB in 50 destinations.  

Customers will be able to track their mobile plan, data usage, monitor roaming and see their mobile spend and their everyday spending in the Monzo app. They will also be able to upgrade their roaming plan or add specific countries to it via the app. 

All the mobile plans available include visual voicemail, wifi calling and the ability to connect other devices via a mobile hotspot.  

For customer service, Monzo says customers will be able to get '24/7 in-app customer support from Monzo with real people on hand.' 

Duygu Yenidogan-Schmidt, general manager for core banking at Monzo, said: 'We’ve always believed your bank should do the hard work for you - now we’re bringing that same thinking to mobile. 

'Monzo Mobile gives you flexibility, reliable coverage and a simple, transparent experience, while rewarding your loyalty. It’s mobile, done the Monzo way.'

Monzo is now Britain's largest digital bank, having welcomed 3million more customers over the last year, bringing its total to 15.2million. 

Customer deposits rose 55 per cent to more than £25billion.