LAST FRIDAY, when others were toiling away as usual in the office, the 5,000 employees of the National Trust were at home changing lightbulbs and making compost toilets on their allotments, writes Lucy Kellaway

The stately homes charity decided to give all its workers February 29th off, and told them to spend it making their own, less stately homes greener. Each was given a list of things they could do: insulate the loft; install a water meter; put a water hippo in the toilet cistern, turn the heating thermostat down and so on.

To ensure that staff were actually doing these things, rather than watching daytime television and getting pizza delivered, they were told to fill in a form saying what they had done, and to take photos of their efforts to prove it. Today, one assumes, they will all be passing around snaps, oohing and aahing over each others' pictures of water meters and close-ups of PVC sealant inserted into draughty gaps.

The scheme sounds a splendid thing. Goodwill is created twice: first by giving staff a day off, and then by getting them to do the things that they knew they ought to do but hadn't found time for. Hearts are warmed quite a lot and the planet is cooled an infinitesimally tiny bit. How many National Trust staff does it take to change a lightbulb? Well, assuming they do one each, that means 5,000 low-energy lightbulbs, which is better than nothing.

Yet the more I think about this great green day, the more uneasy I feel. I like the idea of a day off on leap day: given that companies budget on a 365 day basis, on February 29th, we are really providing our labour for nothing. What I don't like is being told how to spend it.

Particularly I don't like the idea of my employer having anything to do with my set-up at home. The state of my toilet cistern concerns me alone.

In fact, any suggestions on what I do outside work hours are unwelcome. I remember a few years ago all of us at the FTwere given an additional £60 in recognition of our hard work, and were told to use the money to take our partners out to dinner to thank them for their patience.

Even this made me bridle. Don't you tell me what to spend my money on, I thought, and don't presume I have a partner at all, let alone a patient one. I'll spend the whole lot on Bacardi Breezers and drink them all myself, if I feel like it.

But at least it was meant kindly and we weren't asked to bring in receipts for the meal the next day or photos of us as couples smiling at each other across restaurant tables.

Yet at the National Trust the process may go further. The charity is working at ways of making compliance with green schemes part of its appraisal process.

This could mean people who simply changed one lightbulb at home could get promoted more slowly than those who went the whole way and installed solar panels. The end goal - to use less energy - may be admirable.

The means are not: this isn't North Korea.

The National Trust isn't alone in thinking leap day a good day for totalitarianism. Feelgood Drinks put out a press release last week saying that it had told staff not to come into work: "We can all have the day off if we want to . . . as long as we use it to spread some feelgoodness. Seems fair enough!"

Only it doesn't feel fair enough. This announcement makes me more than uneasy - it makes me queasy too.

The march of companies into our lives started a long time ago. Once upon a time the working day used to last from nine to five. But then working hours started getting longer and companies started arranging our childcare and delivering our dry cleaning.

More recently they have taken an interest in our health and fitness or "wellness", as it is now called.

This is sinister, though makes some sense in that sick workers are worse for profits than healthy ones. However, this latest foray into our moral lives is insupportable.

Big companies, especially banks and especially in the US, are leaning heavily on employees to support their charitable initiatives and punishing those that don't. One senior investment banker recently wrote to me in my capacity as office agony aunt complaining that at her annual appraisal she had been told off for not getting involved in the bank's charity work. She felt - quite rightly - indignant.

Two readers wrote in to say that this was mean-spirited and being a moral and rounded manager involved giving time to charity. That's as may be; but it isn't the employer's responsibility. Indeed, if banks really do start appraising employees on the grounds of who has given most time to charity, they may find that they are in even greater financial trouble than they are at present.

Charity has a place in the office, but only when it is closely related to the business. Then it is fine to get staff to join in, but only if they wish to do so. If they don't wish to, that should be fine too.

As for the National Trust, I wonder if combating global warming is absolutely central to what it does. Indeed, if the climate gets a little warmer, that surely will encourage more tourists to the UK, and with the sun shining down they can traipse in ever larger numbers around the stately homes and gardens of Britain.