Lord Brabazon of Tara, the Conservatives' transport spokesman and a former transport minister, used part of his speech to press the case for the motorist. He did not mention that he had links with several transport organisations including the Institute of the Motor Industry, and the Vehicle Security Installation Board.
"Do the Government accept that higher taxes for motorists will affect disproportionately women, the elderly, disabled people and people in rural areas, who regard a car as a necessity and for all of whom safe and secure travelling by car is a major consideration?" he asked.
His speech did not breach the Lords' code for the registering of interests, which is largely voluntary. It does suggest that peers should mention such links when they rise to speak, but no action is taken when they fail to do so. In fact, unlike some other peers, Lord Brabazon mentions all his directorships but one - the Parliamentary Advisory Council on Transport Safety - in the register.
Lord Ezra, a former chairman of the National Coal Board and the Liberal Democrats' energy spokesman, also mentions all his directorships.
He lists a number of power companies, including Energy and Technical Services Group Plc, and told The Independent last week that he was scrupulous about mentioning them in debates even though most members knew his background.
"I have had a previous interest in energy for 50 years, but I always remind the house. It must be very boring," he said.
However, when Lord Ezra introduced a debate on energy policy on 4 June this year he did not explicitly declare an interest.
"While there is no shortage of energy at the present time and prices are relatively low, nevertheless, those of us who have been in the energy business all know that the situation can change very rapidly," he told the house.
Some peers choose not to register any interests. Among them is Lord Pilkington of Oxenford, a Conservative education and employment spokesman who is listed at Companies' House as being on the council of Milton Abbey, an independent school in Dorset. He does not register the unpaid post in the Lords, but in April this year he asked a series of questions on the comparative exam results of schools in the state and independent sectors.
Others argue that they do not always need to declare their interests in debates. When he gave an impassioned speech in favour of offshore wind farms last October Lord Moynihan, formerly the Conservative sport minister Colin Moynihan and now a Foreign Affairs spokesman, declared an interest as president of the British Wind Energy Association. However, he did not mention the Enron Renewable Energy Corporation, a directorship of which is listed on the register.
He told The Independent that although Enron might consider running offshore wind farms in future it had not done so yet because the government had not set up a regime for running them.
"There are no offshore wind energy projects yet. When there are, we may or may not be interested," he said. "My own personal view and the way I apply myself is that both houses should be equally rigorous," he added.
Baroness Miller of Hendon, who speaks on health, trade and industry and the environment for the Conservatives, does not list any directorships in the register of interests. However, she is listed at Companies House as holding investments in Caverwell Property Company and in Multrex Securities, another property development company. She is also listed as having a directorship in Benmill Property Company, a firm of consultants.
In March this year Baroness Miller asked a question about the Landlord and Tenant Act, followed by another in May. She also asked a question in March about business tenancies.
Peers say they use their judgment on which interests to register. Lord Holme, the Liberal Democrats' Northern Ireland spokesman, registers directorships of RTZ, the mining company, and of CRA Ltd but did not mention Brassey's, a defence publisher which he has recently sold out of. He mentioned every interest that might be relevant to his work, he said, but peers needed to earn a living.
"There seems to be an assumption that the Lords' still consists of a lot of hereditary toffs who live off coal mines and estates," he said.
Baroness Hamwee, the Liberal Democrats' local government, housing and planning spokeswoman, declares her post as a Richmond-upon-Thames Councillor and her job as a solicitor. She said she had seen abuses of members' interests in the chamber.