(Sharecast News) - Asda moved up to become the second largest supermarket in Britain in recent weeks, while discounter Aldi overtook Morrisons in terms of shopper numbers.Wall-Mart owned Asda's sales grew 0.1% in the 12 weeks to 24 March compared to the equivalent period last year and it grabbed a market share of 15.4%, according to data compiled by Kantar.Kantar said Asda's performance has been fuelled by attracting a greater number of affluent households and shoppers making more regular trips.This saw it overtake Sainsbury's 15.3% market share as its total till roll shrank 1.8% year on year. Hoping to persuade competition authorities to allow their merger, Sainsbury's and Asda last month offered to sell up to 150 supermarkets, plus a number of convenience stores and petrol stations, to another grocery rival or a new entrant.The only other major grocer to struggle in recent weeks was Morrisons, where sales fell 0.1% giving it a market share of 10.3%.German-owned discounter Aldi welcomes 13m households to its stores in the past 12 weeks, which was more than at Morrisons. Aldi achieved a record market share of 8.0% but remained in fifth place in terms of spending, as while it had more households shopping at its stores, these were smaller and/or cheaper shops. Fellow discounter Lidl was the second fastest growing supermarket, with sales growth accelerating to 5.8% thanks to strong growth was seen in bakery goods, frozen foods and biscuits. Lidl's market share grew 5.6% from 5.3% a year ago.Among the 'big four' supermarkets, Tesco enjoyed the strongest growth, up 0.5% but still saw its market share shrink to 27.4% from 27.6% a year ago due to the rise of the discounters.Fraser McKevitt, consumer head of retail and consumer insight at Kantar, pointed out that the number of sales Tesco completed through a deal increased to 40.1%, which was notable at a time when the level of promotion across the grocery market has fallen to less than 31%, the lowest in a decade.The overall grocery market saw sales growth of 1.4% during the 12-week period.Ocado's market share reached a new high of 1.3% after growth of 5.5% in the period.Said McKevitt: "As both Ocado and Co-op have announced new West London-based rapid delivery systems in the past month, it's clear they are eyeing up the £46bn market of less than £30 top-up shops - of which only a fraction are currently home delivered. However, it remains to be seen if this can be successfully rolled out beyond these initial small areas."