is there a problem with using a 4mm cable off a ring circuit to supply 4 double sockets?

If the load justifies the use of 4mm2 then they problem you've got is that it's applied to a single point on the ring (rather than being distributed around it) - so there's an increased risk of overloading the shorter leg of the ring - unless the point of connection is close to the centre of the ring.

Say it's a 30A load, connected 1/4 of the way around the ring, then you'd expect the long leg to carry 10A and the short leg 20A. Any further loads on the short leg and it would be overloaded.

Supplying the 4 sockets via a 13A fuses spur makes sure that can't happen (but of course is only acceptable if the anticipated load is < 3kW).

- Andy.

thanks for reply its only for bedside sockets so no great load only using 4mm as 32amp mcb.

Obvious answer is to make it a 13A fused spur then - and save yourself the cost of 4mm2 cable

- Andy.