Bad earth in house - how can we solve this?

You most likely live in a rural or semi-rural area and have what is known as a TT system. This means that you have your own earth electrode in your garden somewhere? - there should be a cable that runs from this electrode to the fuseboard. Basically you need a longer or additional earth electrodes fitted and possibly an RCD. If your in an urban area then its most likely to be either PME (TNCS) or TNS, and as such your first port of call would be to contact the Distribution Network Operator for your area (UKPN, SSE, CE, WPD etc)

If you have a TN-C-S(PME) or TN-S(cable sheath earth) call the distribution network operator to sort it out. If you have a TT earthing arrangement(no distributor's earth) then call a registered electrician to rectify. The above information presumes a main earth fault as you have described.

Hi it might not be a bad earth in your house but only a bad earth-bond to your gas pipe. you can have a electrician do a simple test which will tell you about your earth bond and earthing arrangement. If it is a bad incoming earth you might need a earth rod to be installed. It could just be a case of updating earth bonding.

Depends on what earthing system you have. Tns , tncs. Tt are usually residential property

'Earthing' can be a complex affair and would need a competent person equipped with testing equipment to do a thorough check. Although you can physically check the existence of an 'earth' connection and bonding connections at say water, gas, oil services theres not much more you could do as a lay person and the mere existence of those connections doesn't mean you are adequately protected. Best advice: hire someone from mybuilder to inspect and test it for you.