Speaker Lockwood Smith's wife is accompanying MPs on the annual Speaker's tour because she has a "representational role".

The cost of the tour includes business class fares to Europe and $48,000 on hotel bills and incidentals during a two week sweep through Britain, Belgium and Croatia.

Four MPs, Smith's wife, Alexandra, are Smith's secretary are on the trip.

Prime Minister John Key said the MPs were expected to be "cautious" about what they spend - but he doesn't have a problem with the total bill.

"Even in very tight financial times it's worth remembering the Government spends $71 billion a year, so some small expenditure in linking our democracies with others makes sense, but obviously we expect them to be cautious with how they spend."

A spokesperson for the Clerk of the House said the tour was an integral part of New Zealand's inter-parliamentary relations programme.

"Parliaments have a role to play in the sphere of foreign policy, promoting international cooperation and democratic values."

And the New Zealand Government was of great interest internationally.

"The Speaker's delegation is a core element in sharing information about these strengths. Representation from different political parties adds value through reflecting the divergent views of members."

None of the MPs' spouses were travelling with the delegation but the Speaker's wife had a "representational role".

Smith announced the trip last week after the group had left and said it would "invigorate" political and historical ties with Europe.

Other MPs on the trip are National's Melissa Lee, Labour's Darien Fenton, Green MP Gareth Hughes and NZ First MP Denis O'Rourke.

The delegation has been in London for the past few days.

Today it is due to meet with MP Sir Alan Haselhurst, Director Commonwealth and International Relations and Secretary Andrew Tuggey, MP and chair of the Political and Constitutional Reform Committee Graham Allen and Speaker of the House of Lords Baroness D'Souza.

Tomorrow the group flies to Zagreb where it will meet with a number of Croatian politicians and public officials.

- © Fairfax NZ News