Martin Lewis, the Money Saving Expert, has issued a stern warning against being overly loyal to companies you deal with, from banking to utilities.

On his BBC podcast this week, Martin tackled some common financial disputes between couples, such as which credit card to pay off first and how to manage luxury spending.

However, one recurring question led him to reveal what he considers one of the biggest "financial sins".

While offering advice to those experiencing financial disagreements within their relationships, guest Gethin Jones noticed a common thread among the queries. He noted that several couples were debating whether they should remain loyal to certain banks or utility providers.

Without missing a beat, Martin advised households to abandon their loyalty whenever possible, cautioning: "Financial loyalty tends to be a financial sin."

Instead, Martin encouraged people to critically evaluate the products on offer, rather than focusing on who is providing them. He explained that a single company is unlikely to be the best choice for multiple product offerings.

Sharing his personal approach to managing finances, he said: " I personally always focus on the product and not the provider.

"I look at the product, I don't really care who it's with, and I go with the product that's best rather than going with the same bank or organisation. What you want to do is have the best buys in all different product categories. They often do not reward existing customers, existing customers get worse deals," he claimed.

With a hint of optimism, Martin acknowledged that some sectors are "moving a little bit" away from punishing loyalty, but maintained that currently: "Loyalty tends not to pay," and stressed the importance of shopping around to find the best product.