McCullum's deal with the Cyprus-registered company was announced in November 2022, six months after he was appointed to his current role with the England men's side. However, over the past few weeks, adverts on YouTube and posts from the 41-year-old's social media feeds have come under scrutiny, particularly in New Zealand.

In response to McCullum's relationship with Bet22 India, the ECB released the following statement: "We are currently exploring the matter, and [are] in discussions with Brendon around his relationship with the Cypriot-based betting company, 22Bet. We have rules in place around gambling, and will always seek to ensure these are followed."

The ECB's anti-corruption code states "participants" are prohibited from "directly or indirectly enticing, persuading, encouraging or facilitating any other party to enter into a bet in relation to the result, progress, conduct or any other aspect of any match or competition".

Last week, New Zealand's Problem Gambling Foundation filed an official complaint to the country's Department of Internal Affairs (DIA). In response, the DIA confirmed 22Bet's adverts are misleading because "they are not a registered New Zealand sports bookmaker, nor are they licensed or regulated in New Zealand by the DIA".

As a result, adverts featuring McCullum and 22Bet India have been geoblocked for users in the country. The Problem Gambling Foundation also contacted the ECB.

In the adverts, McCullum encourages betting on the IPL. In a video posted on Facebook, he says: "The IPL is coming, and I think all cricket fans are excited for this big event. My friends at 22Bet are ready to make your IPL experience even more fascinating. 22Bet India guarantees the best odds."

McCullum's agent, Simon Auteri told the Times newspaper in a statement: "We are speaking to the ECB about this. I am not going to comment on anything. We are working through it."

Since taking over as head coach, McCullum and captain Ben Stokes have led the Test side to ten wins out of 12, an upturn on their previous run of just one win in 17. McCullum is currently back home in New Zealand, and is due to return to the UK next month, ahead of England's first Test of the summer against Ireland at Lord's, which begins on June 1.